eviction handle walk can race with handle re-open

[1503426122:660745][1403:0x3ff8687f910], t, evict pass: __evict_walk, 1475: btree->root.page != NULL

[1503426122:666457][1403:0x3ff8687f910], t, evict pass: aborting WiredTiger library

*** Aborted

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

#  RUN PARAMETERS

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

abort=0

alter=0

auto_throttle=1

backups=0

bitcnt=5

bloom=1

bloom_bit_count=51

bloom_hash_count=29

bloom_oldest=0

cache=30

checkpoints=1

checksum=uncompressed

chunk_size=1

compaction=0

compression=zlib

data_extend=0

data_source=lsm

delete_pct=2

dictionary=0

direct_io=0

encryption=rotn-7

evict_max=1

file_type=row-store

firstfit=0

huffman_key=0

huffman_value=0

in_memory=0

insert_pct=47

internal_key_truncation=1

internal_page_max=13

isolation=random

key_gap=6

key_max=99

key_min=20

leaf_page_max=14

leak_memory=0

logging=0

logging_archive=0

logging_compression=none

logging_prealloc=0

long_running_txn=0

lsm_worker_threads=3

merge_max=12

mmap=1

modify_pct=25

ops=100000

prefix_compression=1

prefix_compression_min=6

quiet=1

read_pct=19

rebalance=1

repeat_data_pct=4

reverse=0

rows=100000

runs=100

salvage=1

split_pct=71

statistics=0

statistics_server=0

threads=13

timer=20

transaction_timestamps=0

transaction-frequency=41

value_max=972

value_min=16

verify=1

wiredtiger_config=

write_pct=7

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