Fix flaky AudioTrackTest#testPlayStreamData

AudioTrack.release() is not synchronous, wait for it to complete.

Bug: 24340787
Change-Id: Ib391b93223b65631f4ae2d6ea060feff0d9748bf
diff --git a/tests/tests/media/src/android/media/cts/AudioTrackTest.java b/tests/tests/media/src/android/media/cts/AudioTrackTest.java
index 4c03183..9ae6b64 100644
--- a/tests/tests/media/src/android/media/cts/AudioTrackTest.java
+++ b/tests/tests/media/src/android/media/cts/AudioTrackTest.java
@@ -1646,6 +1646,7 @@
                     Thread.sleep(WAIT_MSEC); // wait for the data to drain.
                     // -------- tear down --------------
                     track.release();
+                    Thread.sleep(WAIT_MSEC); // wait for release to complete
                     frequency += 50; // increment test tone frequency
                 }
             }