'Failback group that has been failed back should just return.'

def test_failback_group_that_has_been_failed_back(self):

    self.configuration.replication_device = [TEST_REPLICATION_DEVICE]
    self.driver = FakeDS8KProxy(self.storage_info, self.logger, self.exception, self, TEST_TARGET_DS8K_IP)
    self.driver.setup(self.ctxt)
    group_type = group_types.create(self.ctxt, 'group', {'consistent_group_snapshot_enabled': '<is>    True'})
    group = self._create_group(host=TEST_GROUP_HOST, group_type_id=group_type.id, replication_status='enabled')
    vol_type = volume_types.create(self.ctxt, 'VOL_TYPE', {'replication_enabled': '<is>    True'})
    location = six.text_type({'vol_hex_id': TEST_VOLUME_ID})
    data = json.dumps({TEST_TARGET_DS8K_IP: {'vol_hex_id': TEST_VOLUME_ID}})
    volume = self._create_volume(volume_type_id=vol_type.id, provider_location=location, replication_driver_data=data, group_id=group.id, replication_status='available')
    (model_update, volume_update_list) = self.driver.failover_replication(self.ctxt, group, [volume], 'default')
    self.assertEqual({}, model_update)
    self.assertEqual([], volume_update_list)
