Restore some poor D-Bus methods who got a bit hastily deleted. Enable writing to the "last_checked_ok" property.
* mandos (ClientDBus.CheckedOK, ClientDBus.Enable, ClientDBus.StartChecker, ClientDBus.Disable, ClientDBus.StopChecker): Restored. (ClientDBus.last_checked_ok_dbus_property): Make writing to this property do "self.checked_ok()".