Frameworks: fix notification cancel on privacy guard

new activity stack from google to handle the shiny new launcher
stuff is running on several instances. That said mPrivacyGuardPackageName
currently does not survive when going from an app into launcher. Make
it static to solve it.

Change-Id: Ic9374d2cc58cb716b086365ab8aa96ffaef44879
Signed-off-by: Kristofer Ard <kristoferard@gmail.com>

Conflicts:
	services/java/com/android/server/am/ActivityStack.java