aaudio: unlock when joining the timestamp thread

This will prevent a deadlock in case the timestamp
thread tries to acquire the same lock.

Bug: 182852602
Test: plug and unplug headphones while playing
Change-Id: I625d191906c7e280f3a223f476716ef17b9098ea
diff --git a/services/oboeservice/AAudioServiceStreamBase.cpp b/services/oboeservice/AAudioServiceStreamBase.cpp
index 8638f36..c25a152 100644
--- a/services/oboeservice/AAudioServiceStreamBase.cpp
+++ b/services/oboeservice/AAudioServiceStreamBase.cpp
@@ -336,7 +336,12 @@
 
     setState(AAUDIO_STREAM_STATE_STOPPING);
 
+    // Temporarily unlock because we are joining the timestamp thread and it may try
+    // to acquire mLock.
+    mLock.unlock();
     result = stopTimestampThread();
+    mLock.lock();
+
     if (result != AAUDIO_OK) {
         disconnect_l();
         return result;