The devref was suggesting to do exactly the wrong thing for cases where
we have SQLAlchemy event listeners waiting for deleted objects.
DELETE statements fail to trigger any kind of SQLAlchemy event
listeners and the majority of our delete operations are small
(<10 items at once) so the performance difference is negligible
(especially since we do it so infrequently).
Change-Id: Id142179418a7b94d8d9695871b3fcd5dcc64730c
b87715d764