LSM chunk checkpoints can race with system checkpoints

WT_SESSION.checkpoint: wt-000019.lsm: an unexpected checkpoint start

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#  RUN PARAMETERS

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abort=0

alter=0

auto_throttle=1

backups=0

bitcnt=7

bloom=0

bloom_bit_count=28

bloom_hash_count=16

bloom_oldest=0

cache=60

cache_minimum=20

checkpoints=on

checkpoint_log_size=165

checkpoint_wait=65

checksum=uncompressed

chunk_size=2

compaction=1

compression=zlib

data_extend=0

data_source=lsm

delete_pct=5

dictionary=0

direct_io=0

encryption=rotn-7

evict_max=1

file_type=row-store

firstfit=0

huffman_key=0

huffman_value=0

independent_thread_rng=1

in_memory=0

insert_pct=68

internal_key_truncation=1

internal_page_max=9

isolation=snapshot

key_gap=20

key_max=256

key_min=256

leaf_page_max=9

leak_memory=0

logging=0

logging_archive=0

logging_compression=none

logging_file_max=109418

logging_prealloc=1

long_running_txn=0

lsm_worker_threads=4

merge_max=13

mmap=1

modify_pct=14

ops=100000

prefix_compression=0

prefix_compression_min=4

quiet=1

read_pct=5

rebalance=1

repeat_data_pct=54

reverse=0

rows=100000

runs=1

salvage=1

split_pct=74

statistics=0

statistics_server=0

threads=20

timer=360

transaction_timestamps=1

transaction-frequency=29

truncate=0

value_max=1936

value_min=10

verify=1

wiredtiger_config=

write_pct=8

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