Initial support for specifying which servers to try in joinRoom

This has a bug when using browser-request where the query string for `server_name: [a, b]` comes out as `?server_name=a,b` instead of `?server_name=a&server_name=b`. This is due to browser-request not supporting the same qs options as request, so the qsStringifyOptions do nothing.

src/http-api.js

@@ -668,6 +668,9 @@ module.exports.MatrixHttpApi.prototype = {
      * @param {function=} opts.bodyParser function to parse the body of the
      *    response before passing it to the promise and callback.
      *
+     * @param (object=} opts.qsStringifyOptions options for stringifying the
+     *    query string.
+     *
      * @return {module:client.Promise} a promise which resolves to either the
      * response object (if this.opts.onlyData is truthy), or the parsed
      * body. Rejects
@@ -752,6 +755,8 @@ module.exports.MatrixHttpApi.prototype = {
                     method: method,
                     withCredentials: false,
                     qs: queryParams,
+                    //qsStringifyOptions: opts.qsStringifyOptions,
+                    useQuerystring: true,
                     body: data,
                     json: false,
                     timeout: localTimeoutMs,