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

[automerger skipped] aaudio: unlock when joining the timestamp thread am: 52efb588 am: 9295b214 -s ours am: 9c482137 -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/+/15014351

Change-Id: I11b634271be804745ee9cc5f9713c76ea1f3c239