Start polling in test client upon a successful login

This was removed unintentionally two commits ago.

Signed-off-by: Gergely Polonkai <gergely@polonkai.eu>

src/test-client.c

@@ -77,6 +77,7 @@ login_finished(MatrixClient *client, gboolean success, GMainLoop *loop)
 
     if (success) {
         save_state(client);
+        matrix_client_begin_polling(client, NULL);
     } else {
         g_main_loop_quit(loop);
     }