Websocket: Set disconnected earlier in Shutdown

This caused a possible race where state is still connected, but we start
to trigger interested actors via ShutdownC and Wait.
They may check state and then call Shutdown again, such as
trafficMonitor

exchanges/stream/websocket.go

@@ -477,10 +477,11 @@ func (w *Websocket) Shutdown() error {
 	w.subscriptions = subscriptionMap{}
 	w.subscriptionMutex.Unlock()
 
+	w.setState(disconnected)
+
 	close(w.ShutdownC)
 	w.Wg.Wait()
 	w.ShutdownC = make(chan struct{})
-	w.setState(disconnected)
 	if w.verbose {
 		log.Debugf(log.WebsocketMgr, "%v websocket: completed websocket shutdown", w.exchangeName)
 	}