Don't react if output changes, KRandRTray is not the only boy in town

If you change a config with the KCM and the KRandRTray is executed, when
you change your configuration KRandRTray will react on it and if you
have unityOutput activated, then KRandRTray will force that configuration
invalidating what you (user) did in the KCM.

This is yet another fix in the realm of "Don't do anything unless the
user ask for it".