heap-use-after-free on address in compaction

./configure CCAS=gcc 'CC=clang -fsanitize=address' 'CFLAGS=-g -fno-omit-frame-pointer -I/usr/lib/gcc/ppc64le-redhat-linux/4.8.2/include' --enable-diagnostic --with-builtins=lz4,snappy,zlib --with-berkeleydb=/home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/db

=================================================================

==13388==ERROR: AddressSanitizer: heap-use-after-free on address 0x0a1000045a70 at pc 0x0000103f5e04 bp 0x3fff80f8c660 sp 0x3fff80f8c680

READ of size 8 at 0x0a1000045a70 thread T87

    #0 0x103f5e00 in __wt_ref_info /home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/../src/include/btree.i:1070:18

    #1 0x103f580c in __wt_compact_page_skip /home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/../src/btree/bt_compact.c:189:2

    #2 0x104c5e44 in __tree_walk_internal /home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/../src/btree/bt_walk.c:491:6

    #3 0x104c4714 in __wt_tree_walk /home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/../src/btree/bt_walk.c:678:10

    #4 0x103f35ac in __wt_compact /home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/../src/btree/bt_compact.c:139:3

    #5 0x10349074 in __compact_file /home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/../src/session/session_compact.c:235:3

    #6 0x10346d9c in __wt_session_compact /home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/../src/session/session_compact.c:312:4

    #7 0x10120db4 in compact /home/jenkins/jenkins/workspace/wiredtiger-test-format-stress-sanitizer-ppc/build_posix/test/format/../../../test/format/compact.c:66:14

    #8 0x100eefe8 in __asan::AsanThread::ThreadStart(unsigned long, __sanitizer::atomic_uintptr_t*) /home/mcahill/src/llvm-3.8.1.src/projects/compiler-rt-3.8.1.src/lib/asan/asan_thread.cc:183

    #9 0x100322e8 in asan_thread_start(void*) /home/mcahill/src/llvm-3.8.1.src/projects/compiler-rt-3.8.1.src/lib/asan/asan_interceptors.cc:228

    #10 0x3fff98008940 in start_thread (/lib64/power8/libpthread.so.0+0x8940)

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

#  RUN PARAMETERS

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

abort=0

auto_throttle=1

backups=0

bitcnt=8

bloom=1

bloom_bit_count=8

bloom_hash_count=8

bloom_oldest=1

cache=34

checkpoints=1

checksum=uncompressed

chunk_size=8

compaction=1

compression=lz4-noraw

data_extend=0

data_source=file

delete_pct=12

dictionary=0

direct_io=0

encryption=none

evict_max=5

file_type=row-store

firstfit=0

huffman_key=0

huffman_value=0

in_memory=0

insert_pct=6

internal_key_truncation=1

internal_page_max=9

isolation=random

key_gap=13

key_max=110

key_min=11

leaf_page_max=16

leak_memory=0

logging=1

logging_archive=1

logging_compression=lz4

logging_prealloc=1

long_running_txn=0

lsm_worker_threads=4

merge_max=17

mmap=1

ops=100000

prefix_compression=1

prefix_compression_min=3

quiet=1

repeat_data_pct=50

reverse=0

rows=100000

runs=1

rebalance=1

salvage=1

split_pct=68

statistics=0

statistics_server=0

threads=25

timer=20

transaction-frequency=6

value_max=3265

value_min=17

verify=1

wiredtiger_config=

write_pct=86

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