'Backup an instance in its cell.'

def backup_instance(self, message, instance, image_id, backup_type, rotation):

    instance.refresh()
    instance.task_state = task_states.IMAGE_BACKUP
    instance.save(expected_task_state=[None])
    self.compute_rpcapi.backup_instance(message.ctxt, instance, image_id, backup_type, rotation)
