Handle Galera deadlock on SELECT FOR UPDATE

Using nova-api in the wild shows that we've got an additional
exception, that must be treated like a deadlock, so that we
can handle this error properly and retry the transaction.

Closes-Bug: #1394298

Change-Id: If75f2b5984979fe55ad04ccec8713989307c56ae
Merge "Handle Galera deadlock on SELECT FOR UPDATE"