Revert "Ensures cleanup of transactions that failed to commit is under a lock"

This reverts commit 31eab0c44d7aebd8826b673af7453421d0371089.
Ensures cleanup of transactions that failed to commit is under a lock

Adds a synchronized block around commit and rollback in case of failure
 in TxManager. This ensures that a transaction has the chance to clean up
 its state atomically, preventing a class of errors encountered in HA settings.

Previous commit 31eab0c44d7aebd8826b673af7453421d0371089 that tried the same
 thing was completely wrong, this is a rewrite