message: Don't retry joins if the failure isn't a 5XX
diff: @@ -535,7 +535,7 @@ IrcHandler.prototype.onJoin = Promise.coroutine(function*(req, server, joiningUs
  const joinRetry = (attempts) => {
  req.log.debug(`Joining room (attempts:${attempts})`);
  return intent.join(room.getId()).catch((err) => {
  - if (err.httpStatus <= 500) {
  + if (err.httpStatus === undefined || err.httpStatus <= 500) {
  req.log.error(`Not retrying join for ${room.getId()}.`);
  return Promise.reject(err);
  }
  