Pierre-Yves David <pierre-yves.david@fb.com> [Tue, 28 Oct 2014 14:24:43 +0100] rev 23220
transaction: allow registering a post-close callback
The addchangegroup code considers the transaction done after a 'tr.close()' call
and schedules the hook's execution for after lock release. In the nested transaction
case, the transaction is not yet committed and we must delay this scheduling.
We add an 'addpostclose' method (like the 'addpending' and 'addfinalize' ones) that
registers code to be run if the transaction is successfully committed.