Update worker config when changing worker URL so that timeouts log properly

Without this, the log for timeouts would always show the initial URL, which
can change when running multiple pages per worker.

Author: jzaefferer

lib/server.js

@@ -167,6 +167,7 @@ exports.Server = function Server(bsClient, workers) {
       }
       url += '_worker_key=' + worker._worker_key + '&_browser_string=' + getTestBrowserInfo(worker) ;
       worker.test_path = next_path;
+      worker.config.url = next_path;
       bsClient.changeUrl(worker.id, {url: url}, function() {
         callback(true);
       });