Cleanup AudioTrack::getMinFrameCount error handling

Guarantee to return a non-zero frameCount for return status NO_ERROR;

Return the correct specific status_t if any of the AudioSystem APIs fail,
instead of the generic NO_INIT.

API change: getMinFramCount no longer defaults to zero on error, so
callers _must_ check the return status.  This change makes
getMinFrameCount more like other APIs.  All known callers were reviewed,
and they do check the return status.

Change-Id: I4a8342a75ee89a068c23c84b8380ed9d1b968507
diff --git a/include/media/AudioTrack.h b/include/media/AudioTrack.h
index 9f631cf..8afcc5d 100644
--- a/include/media/AudioTrack.h
+++ b/include/media/AudioTrack.h
@@ -123,6 +123,8 @@
      *  - NO_ERROR: successful operation
      *  - NO_INIT: audio server or audio hardware not initialized
      *  - BAD_VALUE: unsupported configuration
+     * frameCount is guaranteed to be non-zero if status is NO_ERROR,
+     * and is undefined otherwise.
      */
 
     static status_t getMinFrameCount(size_t* frameCount,