Disabling user activity now resets user power state so the keyguard can set...

Disabling user activity now resets user power state so the keyguard can set short screen timeout when keyguard is unhidden.

This is part of a fix for bug b/2248320 (Lock screen does not time out after

Change-Id: Iba7f8a7b9997ecb0e4da37667600055f9a35531c
Signed-off-by: Mike Lockwood <lockwood@android.com>