format configures too-small LSM caches.

nice ./t -1 -c ../../../test/format/CONFIG.stress file_type=row leaf_page_max=9 internal_page_max=9 key_min=256 value_min=256 cache=10

[1524334538:524918][26442:0x7f2865d3e7c0], t, WT_SESSION.create: LSM cache size 20971520 (20MB) too small, must be at least 31488000 (31MB): Invalid argument

t: process 26442

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

#  RUN PARAMETERS

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

abort=0

alter=0

auto_throttle=1

backups=0

bitcnt=7

bloom=1

bloom_bit_count=12

bloom_hash_count=8

bloom_oldest=0

cache=20

cache_minimum=20

checkpoints=on

checkpoint_log_size=197

checkpoint_wait=51

checksum=uncompressed

chunk_size=10

compaction=1

compression=none

data_extend=0

data_source=lsm

delete_pct=2

dictionary=0

direct_io=0

encryption=rotn-7

evict_max=5

file_type=row-store

firstfit=0

huffman_key=0

huffman_value=0

independent_thread_rng=0

in_memory=0

insert_pct=2

internal_key_truncation=1

internal_page_max=9

isolation=read-committed

key_gap=16

key_max=256

key_min=256

leaf_page_max=9

leak_memory=0

logging=0

logging_archive=1

logging_compression=none

logging_file_max=213624

logging_prealloc=1

long_running_txn=0

lsm_worker_threads=3

merge_max=20

mmap=1

modify_pct=66

ops=0

prefix_compression=0

prefix_compression_min=1

prepare=0

quiet=1

read_pct=5

rebalance=1

repeat_data_pct=74

reverse=0

rows=1000000

runs=1

salvage=1

split_pct=52

statistics=1

statistics_server=0

threads=19

timer=4

timing_stress_checkpoint=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

transaction_timestamps=0

transaction-frequency=67

truncate=0

value_max=1382

value_min=256

verify=1

wiredtiger_config=

write_pct=25

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

t: FAILED: wts_init/498: session->create(session, g.uri, config): table:wt: Invalid argument