Tweak TestStatistics suite diagnostics, readability, and resilience to a recurring LiveClients race condition.
Merge pull request #1869 from VoltDB/master

backmerge of master TO test fix branch.
Merge pull request #1872 from VoltDB/master

another backmerge TO TestStatisticsFlakes
Resolved review comments r=cwolff
Merge pull request #1870 from VoltDB/TestStatisticsFlakes

Test statistics flakes