Rollback master backend on all exceptions in multi backend

Some exceptions passed out of backends are not Designate exceptions,
these exceptions are not caught in the multi backend, causing the
rollback code not to be executed.

Change-Id: I9f29b06dcca5ea03f522ae392401ce8b34121e34
Closes-Bug: 1293101
Merge "Rollback master backend on all exceptions in multi backend"