Fix message handling for autostart.

Current implementation of libdbus Request name is blocking, consequently
the first incomming message that triggered the service autostart is not
being processed properly.
diff --git a/gdbus/mainloop.c b/gdbus/mainloop.c
index a06ed22..bd775f8 100644
--- a/gdbus/mainloop.c
+++ b/gdbus/mainloop.c
@@ -272,6 +272,9 @@
 
 	setup_dbus_with_main_loop(conn);
 
+	if (dbus_connection_get_dispatch_status(conn) == DBUS_DISPATCH_DATA_REMAINS)
+		g_timeout_add(DISPATCH_TIMEOUT, message_dispatch_cb, conn);
+
 	return conn;
 }