SEBA-301 Only save changed state

Change-Id: I177e2d6eee878551cc2236deabfddc920a553868
diff --git a/xos/synchronizer/model_policies/test_model_policy_att_workflow_driver_serviceinstance.py b/xos/synchronizer/model_policies/test_model_policy_att_workflow_driver_serviceinstance.py
index afa4183..306094c 100644
--- a/xos/synchronizer/model_policies/test_model_policy_att_workflow_driver_serviceinstance.py
+++ b/xos/synchronizer/model_policies/test_model_policy_att_workflow_driver_serviceinstance.py
@@ -88,7 +88,7 @@
 
             self.policy.update_onu("brcm1234", "DISABLED")
             self.assertEqual(onu.admin_state, "DISABLED")
-            onu_save.assert_called_with(always_update_timestamp=True)
+            onu_save.assert_called_with(always_update_timestamp=True, update_fields=['admin_state', 'serial_number', 'updated'])
 
 
     def test_enable_onu(self):