Cleanup theme assets when done with them

Before this patch if phone was left on long enough it would reboot
when a theme was applied due to files being left open.

Change-Id: I4c242249fcf6e8097789c3dd6690104296485784

Conflicts:
	services/java/com/android/server/NotificationManagerService.java

Conflicts:
	services/java/com/android/server/NotificationManagerService.java