Swap the order of creating IAudioTrack and thread

Simplifies the error recovery in case IAudioTrack fails.

Change-Id: I6aee41a2ac747a5689fb4836b04174e6107bf32f
diff --git a/include/media/AudioTrack.h b/include/media/AudioTrack.h
index 26a25b0..4488ce4 100644
--- a/include/media/AudioTrack.h
+++ b/include/media/AudioTrack.h
@@ -473,7 +473,7 @@
         friend class AudioTrack;
         virtual bool        threadLoop();
         AudioTrack& mReceiver;
-        ~AudioTrackThread();
+        virtual ~AudioTrackThread();
         Mutex               mMyLock;    // Thread::mLock is private
         Condition           mMyCond;    // Thread::mThreadExitedCondition is private
         bool                mPaused;    // whether thread is currently paused