Add AutoCommitUpdate class and replace some onTransactionIdle callers

Add AutoCommitUpdate class and replace some onTransactionIdle callers

* This puts the complex logic here after the commit step for
  all DBs, making the main multi-DB transaction more likely
  to be atomic.
* Made some cleanups to AtomicSectionUpdate and made it cancel
  if the transaction is rolled back as it should.
* Also cleaned up some closures for PHP 5.4.

Change-Id: If2f7bb6b1ba6daf1cfdc934f27c32b0b10431a3d