Did the following fix/modification to make the tests pass:
* Raise an exception on deleting non-existent pod or service.
* Rename the following methods:
get_service_by_bay_uuid -> get_services_by_bay_uuid (db)
get_by_bay_uuid -> list_by_bay_uuid (objects)
Change-Id: I7cbeb119550acecdbf0697df19172a8285eabca8