Fix android.media.cts.ClearKeySystemTest.testClearKeyPlayback

 Add missing audioBuffer.clear() to CodecState.java to fix AudioTrack.write() failures.

Bug:23273860
Change-Id: If238142a67b70e7aa6f0680d5b75bb0166e1b5d2
diff --git a/tests/tests/media/src/android/media/cts/CodecState.java b/tests/tests/media/src/android/media/cts/CodecState.java
index 8494a74..6fdbd86 100644
--- a/tests/tests/media/src/android/media/cts/CodecState.java
+++ b/tests/tests/media/src/android/media/cts/CodecState.java
@@ -330,6 +330,7 @@
             buffer.clear();
             ByteBuffer audioBuffer = ByteBuffer.allocate(buffer.remaining());
             audioBuffer.put(buffer);
+            audioBuffer.clear();
 
             mAudioTrack.write(audioBuffer, info.size, info.presentationTimeUs*1000);