Bug #1261894: Deleting Record With BIND 9 Driver Fails

Fix the delete_record/delete_recordset method so it deletes the
record/recordset in the central storage before the BIND 9 backend
gets the request to delete the record/recordset.

Changed the other delete_<object> methods (quota, server, etc.) with the
same fix.  Finally, all the delete_<object> methods in the storage have
been simplified and make less SQL calls by returning the object from the
delete_<object> method instead of making another get_<object> call.

Change-Id: I10ceb1f5c2550724f1a752a79319a4bbf366876b
Closes-bug: #1261894
Merge "Bug #1261894: Deleting Record With BIND 9 Driver Fails"