vm: simplify shutdown call

circle/vm/operations.py

@@ -723,7 +723,7 @@ class SaveAsTemplateOperation(InstanceOperation):
 
         if with_shutdown:
             try:
-                ShutdownOperation(self.instance).call(parent_activity=activity,
+                self.instance.shutdown(parent_activity=activity,
                                        user=user, task=task)
             except Instance.WrongStateError:
                 pass