Fix Coverity warning:

>>>     CID 1192605:  Resource leak  (RESOURCE_LEAK)
>>>     Handle variable "fd" going out of scope leaks the handle.
When compacting, set the smallest timeout to start them in paralel, then
wait for them to complete.
Add warmup configuration option to wtperf.
Fix wtperf warmup phase to execute mixes workloads.
Merge branch 'develop' into new-split