Make mIsDeviceLockedForUser synchronized. am: 8696c2ca1b am: 19e17f0981 am: f7d50266fc

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/security/+/12855595

Change-Id: I5e831eeb92b3da21cd5ec863141de205b9568732