For ENG-5523, fix SimpleClientResponse adapter to allow callback reuse and pick up multiple responses
For ENG-5523, works better when you don't drop callback on the floor
Merge pull request #970 from VoltDB/ENG-5523

Eng 5523 fix broken SnapshotUtil request snapshot dropping info on queued snapshots
Make csvbenchmark check that the data file size is correct and regenerate if it
isn't.
Oops.  I thought I had stashed these files.
Merge branch 'master' into ENG-5486-null-lessthan