Fix a bug where uncommitted updates could be discarded

==19247==ERROR: AddressSanitizer: heap-use-after-free on address 0x604000fdcad0 at pc 0x0000007a9474 bp 0x7ffbf27ee0b0 sp 0x7ffbf27ee0a8

READ of size 8 at 0x604000fdcad0 thread T15

    #0 0x7a9473 in __wt_txn_rollback /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/txn/txn.c:1313:5

    #1 0x720a61 in __session_rollback_transaction /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/session/session_api.c:1817:2

    #2 0x52b932 in rollback_transaction /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/ops.c:481:2

    #3 0x51f0bd in ops /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/ops.c:1031:12

    #4 0x4dde52 in __asan::AsanThread::ThreadStart(unsigned long, __sanitizer::atomic_uintptr_t*) (/work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/t+0x4dde52)

    #5 0x7ffbfdd3a36c in start_thread (/lib64/libpthread.so.0+0x736c)

    #6 0x7ffbfcf0eb4e in __GI___clone (/lib64/libc.so.6+0x110b4e)

0x604000fdcad0 is located 0 bytes inside of 38-byte region [0x604000fdcad0,0x604000fdcaf6)

freed by thread T32 here:

    #0 0x4d01e8 in __interceptor_free.localalias.0 (/work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/t+0x4d01e8)

    #1 0x6544d9 in __wt_free_int /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/os_common/os_alloc.c:327:2

    #2 0x85fdb2 in __wt_free_update_list /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/bt_discard.c:444:3

    #3 0x861077 in __free_update /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/bt_discard.c:426:5

    #4 0x85e4fe in __free_page_modify /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/bt_discard.c:211:4

    #5 0x85c92d in __wt_page_out /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/bt_discard.c:112:3

    #6 0x85bc48 in __wt_ref_out /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/bt_discard.c:44:2

    #7 0x608ad5 in __evict_page_dirty_update /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/evict/evict_page.c:442:5

    #8 0x6037fe in __wt_evict /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/evict/evict_page.c:205:3

    #9 0x6020e1 in __wt_page_release_evict /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/evict/evict_page.c:83:8

    #10 0x92d052 in __wt_sync_file /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/bt_sync.c:328:5

    #11 0x7ba879 in __checkpoint_tree /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/txn/txn_ckpt.c:1678:3

    #12 0x7c3142 in __checkpoint_tree_helper /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/txn/txn_ckpt.c:1796:8

    #13 0x7c2f33 in __checkpoint_apply /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/txn/txn_ckpt.c:217:3

    #14 0x7bd22f in __txn_checkpoint /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/txn/txn_ckpt.c:908:2

    #15 0x7b8b60 in __txn_checkpoint_wrapper /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/txn/txn_ckpt.c:1107:8

    #16 0x7b8479 in __wt_txn_checkpoint /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/txn/txn_ckpt.c:1171:3

    #17 0x724e36 in __session_checkpoint /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/session/session_api.c:2047:8

    #18 0x539bfe in checkpoint /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/util.c:563:3

    #19 0x4dde52 in __asan::AsanThread::ThreadStart(unsigned long, __sanitizer::atomic_uintptr_t*) (/work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/t+0x4dde52)

previously allocated by thread T15 here:

    #0 0x4d05a8 in calloc (/work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/t+0x4d05a8)

    #1 0x652d20 in __wt_calloc /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/os_common/os_alloc.c:52:11

    #2 0x985209 in __wt_update_alloc /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/row_modify.c:290:3

    #3 0x983122 in __wt_row_modify /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/row_modify.c:97:4

    #4 0x83e0c6 in __cursor_row_modify /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/bt_cursor.c:446:10

    #5 0x840157 in __wt_btcur_remove /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/btree/bt_cursor.c:1089:7

    #6 0xa27c14 in __curfile_remove /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/cursor/cur_file.c:409:2

    #7 0x525d1d in row_remove /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/ops.c:1832:9

    #8 0x51daa9 in ops /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/ops.c:857:11

    #9 0x4dde52 in __asan::AsanThread::ThreadStart(unsigned long, __sanitizer::atomic_uintptr_t*) (/work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/t+0x4dde52)

Thread T15 created by T0 here:

    #0 0x433890 in pthread_create (/work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/t+0x433890)

    #1 0x6707f0 in __wt_thread_create /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/os_posix/os_thread.c:30:2

    #2 0x519826 in wts_ops /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/ops.c:173:3

    #3 0x5341ff in main /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/t.c:221:5

    #4 0x7ffbfce1e889 in __libc_start_main (/lib64/libc.so.6+0x20889)

Thread T32 created by T0 here:

    #0 0x433890 in pthread_create (/work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/t+0x433890)

    #1 0x6707f0 in __wt_thread_create /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/os_posix/os_thread.c:30:2

    #2 0x519b13 in wts_ops /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/ops.c:188:3

    #3 0x5341ff in main /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/test/format/../../../test/format/t.c:221:5

    #4 0x7ffbfce1e889 in __libc_start_main (/lib64/libc.so.6+0x20889)

SUMMARY: AddressSanitizer: heap-use-after-free /work/jenkins/workspace/wiredtiger-test-race-condition-stress-sanitizer/build_posix/../src/txn/txn.c:1313:5 in __wt_txn_rollback

############################################

#  RUN PARAMETERS

############################################

abort=0

alter=0

assert_commit_timestamp=0

assert_read_timestamp=0

auto_throttle=1

backups=0

bitcnt=8

bloom=1

bloom_bit_count=21

bloom_hash_count=27

bloom_oldest=0

cache=88

cache_minimum=20

checkpoints=on

checkpoint_log_size=160

checkpoint_wait=51

checksum=uncompressed

chunk_size=10

compaction=0

compression=snappy

data_extend=0

data_source=file

delete_pct=34

dictionary=0

direct_io=0

encryption=none

evict_max=0

file_type=row-store

firstfit=0

huffman_key=0

huffman_value=0

independent_thread_rng=1

in_memory=0

insert_pct=2

internal_key_truncation=1

internal_page_max=11

isolation=snapshot

key_gap=8

key_max=121

key_min=13

leaf_page_max=12

leak_memory=0

logging=0

logging_archive=0

logging_compression=none

logging_file_max=331783

logging_prealloc=0

long_running_txn=0

lsm_worker_threads=4

memory_page_max=2

merge_max=7

mmap=1

modify_pct=10

ops=0

prefix_compression=0

prefix_compression_min=0

prepare=0

quiet=1

read_pct=1

rebalance=1

repeat_data_pct=8

reverse=1

rows=1000000

runs=1

salvage=1

split_pct=61

statistics=0

statistics_server=0

threads=22

timer=4

timing_stress_aggressive_sweep=0

timing_stress_checkpoint=0

timing_stress_lookaside_sweep=0

timing_stress_split_1=0

timing_stress_split_2=0

timing_stress_split_3=1

timing_stress_split_4=1

timing_stress_split_5=1

timing_stress_split_6=0

timing_stress_split_7=1

timing_stress_split_8=0

transaction_timestamps=1

transaction-frequency=100

truncate=1

value_max=1780

value_min=6

verify=1

wiredtiger_config=

write_pct=53

############################################