Merge "Add read-write lock for per-user operations." am: 18e8bbb4d0 am: b00e5af674 am: beaca83f00

Original change: https://android-review.googlesource.com/c/platform/frameworks/native/+/1901110

Change-Id: Ifcf03c0136afeb6cde05b86522bf7013eaf1e94d