[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: 58ca51f1 -s ours am: 14785ddf -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: Ib9104e96120c22acf3b286ccc7f4175a14688674