Catch websocket connection close errors in cleanup

This can add useless noise when we have timeouts in particular.

Change-Id: I55d18885f06e530ff9a5492c0b98f37525e88ed6
Closes-Bug: #1805647

tripleoclient/plugin.py

@@ -167,7 +167,10 @@ class WebsocketClient(object):
 
     def __exit__(self, *exc):
         """Call cleanup when exiting the context manager"""
-        self.cleanup()
+        try:
+            self.cleanup()
+        except websocket.WebSocketConnectionClosedException:
+            pass
 
 
 class ClientWrapper(object):