ENG-4384: Add a CLI arg to disable adhoc writes in txnId-selfcheck2.
ENG-4384: Add a naive rate limiter to txnId-selfcheck2.
ENG-4384: Set spHandle on CompleteTransactionMessage.

CompleteTransactionMessages truncates the FragmentTaskMessages in the repair
log. On SPI repair, if the complete message doesn't have the latest spHandle,
the new master may generate an spHandle that's already been used before. Set the
spHandle for each complete message so that they can advance the max seen
spHandle on repair.
ENG-4384: Move txnId-selfcheck2 permit reset code to the rate limiter per John's
review.
Merge pull request #387 from VoltDB/ENG-4384

ENG-4384: Modifications to txnId-selfcheck2 for DR tests