WebSockets: increase maximum retries to 9.

This increases the total time it'll try to reconnect up to 34 minutes
from 17.  Experience with a couple of issues with stunnel have shown it
takes a few minutes for everything to settle back down and we do want
everyone to get reconnected eventually without having to refresh.

r2/r2/public/static/js/websocket.js

@@ -9,7 +9,7 @@ r.WebSocket = function (url) {
 }
 _.extend(r.WebSocket.prototype, Backbone.Events, {
     _backoffTime: 2000,
-    _maximumRetries: 8,
+    _maximumRetries: 9,
 
     _connect: function () {
         r.debug('websocket: connecting')