KCM: better handle revert timer and buttons
The issue was that the revertSettings method was called when the timer timed out, the settings were reverted, the confirmMsg overlay closed and called a second time revertSettings when the kcm backend has not been reloaded yet.
This makes sure this won't happen, as either the timer of the revert button will revert the Settings but not simply closing `confirmMsg. This makes the code simpler by removing book keeping but instead using only the events.