For ENG-5498, do leader appointer promotion from the correct thread
For ENG-5498, fix deadlock
For ENG-5498, move deeper down the rabbit hole of asynchronicity. There is a bottle, with a note that says drink me
For ENG-5498, suppress shutdown errors, fix test cases
For ENG-5498, add comments based on feedback
Merge pull request #945 from VoltDB/ENG-5498

For ENG-5498, do leader appointer promotion from the correct thread
Reverting "ENG-5471 REVERT BEFORE RELEASE: Sanity check balance partitions by
doing a table scan at the end of each @BalancePartitions call."

This reverts commit 784a76a56250f139f3782ac21a305cf62340577e.
Merge branch 'master' into ENG-5459