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

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

Change-Id: I59d44fcd72c13fb9b6a954330d3a45bda966e83f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>