Merge "UMS use mUsersLock to synchronized" am: 659ccfc928 am: ca2d0638ab

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1512949

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I9075ab382ff6d8cb35c9fae6a776797887332c12