Merge pull request #1667 from nanoric/fix_docstring

[Mod] 修正了一下websocket_client的stop和join的注释

vnpy/api/websocket/websocket_client.py

@@ -88,8 +88,6 @@ class WebsocketClient(object):
     def stop(self):
         """
         Stop the client.
-
-        This function cannot be called from worker thread or callback function.
         """
         self._active = False
         self._disconnect()
@@ -97,6 +95,8 @@ class WebsocketClient(object):
     def join(self):
         """
         Wait till all threads finish.
+
+        This function cannot be called from worker thread or callback function.
         """
         self._ping_thread.join()
         self._worker_thread.join()