DatabaseEngine.updateEntity always drops/adds foreign keys even if the schema didn't change

[fdz-joaomiguel]

The expected behavior of DatabaseEngine.updateEntity, with schema policy create, is that if the entity does not need to be updated no DDL is executed; however, the current implementation (in AbstractDatabaseEngine) is always dropping all foreign keys at the beginning and adding them back at the end.
Calling DatabaseEngine.updateEntity should be a no-op if the entity did not change.