Further optimize dictupdate.update()

salt/utils/dictupdate.py

@@ -28,6 +28,8 @@ def update(dest, upd, recursive_update=True):
     '''
     if dest is None:
         return upd
+    if not (set(dest.keys()) & set(upd.keys())):
+        recursive_update = False
     if recursive_update:
         for key, val in six.iteritems(upd):
             try: