Merge "snapuserd: Fix race condition in MergeWorker::WaitForMergeBegin." into main am: c718295a58 am: 9077049910 am: d17c3ebb40 am: 0e05170078 am: 95b3d2e69a

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2701653

Change-Id: I42afb645d59cf31019df4df125e226faa77b1fe3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>