[automerger skipped] aaudio: unlock when joining the timestamp thread am:...

[automerger skipped] aaudio: unlock when joining the timestamp thread am: 5f6fda77 am: dc90f241 -s ours

am skip reason: Merged-In I625d191906c7e280f3a223f476716ef17b9098ea with SHA-1 5f6fda77 is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/14937760

Change-Id: If8d3d88e4cace7010804bab8b8e3e34d0af7b6bb