Keyguard: don't refresh ui when screen off

KeyguardStatusView is doing refresh all the time,
which cause high power when screen off.

PatchSet:
- We turn of the refresh when screen is off which is a good
  idea. But we should force latest next refresh when screen turns
  on. Du that a timechanged refresh maybe comes a bit later.

Change-Id: Icbb9a92bae3cf099417ab820617dd3f17e49f75a
Forward Port: Volume button seek on screen off [1/2]

PS : Fix the short press event type

Change-Id: Id55a1240a133b5144502fced862bae040b390662

Conflicts:
	core/java/android/provider/Settings.java