Recent changes affect LSM performance

Something in the very large set of changes during this Jenkins run results in a very large negative impact on most LSM performance runs. Parallel populate time went from 21 to 70. Update-lsm insert throughput dropped from 40M to 14M (without any respective increase in read/update throughput).

http://build.wiredtiger.com:8080/job/wiredtiger-perf-lsm/533/