[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 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: Ib9af09c5a38bc6653a1840a1ee6f992de2b2bcca