vm: yield vnc port only at destroy

circle/vm/models/instance.py

@@ -459,10 +459,6 @@ class Instance(AclBase, VirtualMachineDescModel, StatusModel, OperatedMixin,
         except ActivityInProgressError:
             pass  # discard state change if another activity is in progress.
         else:
-            if new_state == 'STOPPED':
-                self.vnc_port = None
-                self.node = None
-                self.save()
             act.finished = act.started
             act.resultant_state = new_state
             act.succeeded = True

circle/vm/operations.py

@@ -629,7 +629,6 @@ class ShutdownOperation(InstanceOperation):
     def _operation(self, task=None):
         self.instance.shutdown_vm(task=task)
         self.instance.yield_node()
-        self.instance.yield_vnc_port()
 
     def on_abort(self, activity, error):
         if isinstance(error, TimeLimitExceeded):
@@ -670,9 +669,7 @@ class ShutOffOperation(InstanceOperation):
         with activity.sub_activity('delete_vm'):
             self.instance.delete_vm()
 
-        # Clear node and VNC port association
         self.instance.yield_node()
-        self.instance.yield_vnc_port()
 
 
 register_operation(ShutOffOperation)