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

[automerger skipped] aaudio: unlock when joining the timestamp thread am: 5f6fda77 am: ad47e0a3 -s ours am: 5eb61d06 -s ours

am skip reason: Merged-In I625d191906c7e280f3a223f476716ef17b9098ea with SHA-1 d50ae62f is already in history

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

Change-Id: I200336d29d555a6eec3518059fe336ae2605887f