ENG-4264: Change ReplaySequencer to have an explicit drain() method to
get stuff that will be ignored at the command log replay tail.  Add
additional unit tests.
Merge remote-tracking branch 'origin/master' into eng4264

Conflicts:
	src/frontend/org/voltdb/iv2/SpScheduler.java
ENG-4264: Yay code review.  Add a test case and a fix for a defect
nshi found.
Merge pull request #356 from VoltDB/eng4264

Eng4264