Make mIsDeviceLockedForUser synchronized. am: c7431a287b am: eed15b0281 am: 4d003d09ce

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/security/+/12855494

Change-Id: I6c9e2d3f9ded91ae91999a5762a46092a33cd437