stop client websocket close echoing server close
Client initiated close requests should send a close message to the
server that the server will echo back to complete the process. Servo
should not then echo the servers close request back again to the server,
this guard stops servo from echoing a server close request if the
process was initiated by the client.
Tracked in https://github.com/servo/servo/issues/9803#issuecomment-196424406
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96f3404928
