manager: Don't log when we're exiting

This happens on hardware without fingerprint readers on every boot; we
don't need to log anything about it, it's totally normal.

This patch is part of an initiative to reduce logging spew in GNOME
so that actual errors and important messages are more visible.

https://bugs.freedesktop.org/show_bug.cgi?id=71889

src/manager.c

@@ -79,7 +79,6 @@ static gchar *get_device_path(FprintDevice *rdev)
 static gboolean
 fprint_manager_timeout_cb (FprintManager *manager)
 {
-	g_message ("No devices in use, exit");
 	//FIXME kill all the devices
 	exit(0);
 	return FALSE;