SegFault while freeing WT_REF address during page eviction

++ SEGFAULT_SIGNALS=all

++ nice catchsegv ./t -1 -c ../../../test/format/CONFIG.stress file_type=row leaf_page_max=9 internal_page_max=9 key_min=256 value_min=256

*** Error in `./t': invalid fastbin entry (free): 0x00003fff305f55d0 ***

(...)

Backtrace:

/lib64/libSegFault.so(+0x1734)[0x3fff9a371734]

??:0(??)[0x3fff9a3a0478]

/lib64/power8/libc.so.6(abort+0x27c)[0x3fff9a07072c]

/lib64/power8/libc.so.6(+0x84aa4)[0x3fff9a0b4aa4]

/lib64/power8/libc.so.6(+0x8fe94)[0x3fff9a0bfe94]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/os_common/os_alloc.c:327(__wt_free_int)[0x1008cfac]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/include/btree.i:680 (discriminator 1)(__wt_ref_addr_free)[0x1014dda8]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/btree/bt_discard.c:273(__wt_free_ref)[0x1014eb48]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/btree/bt_discard.c:293(__free_page_int)[0x1014ecc0]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/btree/bt_discard.c:120(__wt_page_out)[0x1014e4a4]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/btree/bt_discard.c:45(__wt_ref_out)[0x1014e170]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/evict/evict_page.c:445(__evict_page_dirty_update)[0x100730b8]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/evict/evict_page.c:205(__wt_evict)[0x10071d28]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/evict/evict_lru.c:2414(__evict_page)[0x1006dbc8]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/evict/evict_lru.c:1200(__evict_lru_pages)[0x100698e0]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/evict/evict_lru.c:337(__wt_evict_thread_run)[0x10067668]

/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-ppc/build_posix/../src/support/thread_group.c:31(__thread_run)[0x100f8578]

/lib64/power8/libpthread.so.0(+0x8944)[0x3fff9a2c8944]

/lib64/power8/libc.so.6(clone+0x98)[0x3fff9a147640] 

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

#  RUN PARAMETERS

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

abort=0

alter=1

assert_commit_timestamp=0

assert_read_timestamp=0

auto_throttle=1

backups=0

bitcnt=6

bloom=1

bloom_bit_count=44

bloom_hash_count=14

bloom_oldest=0

cache=468

cache_minimum=20

checkpoints=wiredtiger

checkpoint_log_size=50

checkpoint_wait=16

checksum=uncompressed

chunk_size=7

compaction=0

compression=snappy

data_extend=0

data_source=table

delete_pct=1

dictionary=0

direct_io=0

encryption=none

evict_max=3

file_type=row-store

firstfit=0

huffman_key=0

huffman_value=0

independent_thread_rng=0

in_memory=0

insert_pct=0

internal_key_truncation=1

internal_page_max=9

isolation=random

key_gap=10

key_max=256

key_min=256

leaf_page_max=9

leak_memory=0

logging=1

logging_archive=0

logging_compression=zlib

logging_file_max=422025

logging_prealloc=0

long_running_txn=0

lsm_worker_threads=4

memory_page_max=9

merge_max=8

mmap=1

modify_pct=0

ops=0

prefix_compression=1

prefix_compression_min=3

prepare=0

quiet=1

read_pct=59

rebalance=1

repeat_data_pct=11

reverse=0

rows=1000000

runs=1

salvage=1

split_pct=70

statistics=1

statistics_server=0

threads=26

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=0

timing_stress_split_4=0

timing_stress_split_5=0

timing_stress_split_6=0

timing_stress_split_7=0

timing_stress_split_8=0

transaction_timestamps=0

transaction-frequency=50

truncate=1

value_max=3024

value_min=256

verify=1

wiredtiger_config=

write_pct=40

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