frameworks/av: Set key mimetype for audio only ASF and 3gp clips

- Parse function used while scanning the media information is
  not able to get the proper mimetype for ASF clips. Since
  ASF clips are considered as video clips by default based on
  the file extention audio only clips are also visible in
  video application and not in music application.
- Clip which has AAC audio data but with .3gp extension is not
  detected as audio file and shown as video file.

- Key Mimetype is not updated for ASF clips and retriever
  return mimetype as NULL.
- MIMETYPE for audio only 3GPP is set to video/3gpp and hence
 shown as video clip.

- Check the track information for single track ASF clips and
  set key mimetype to wma for audio only clips so that parse
  function can detect them as audio clips while scanning.
- MIMETYPE for AAC audio clip with .3gpp extension is set to
  audio/aac to detect it as audio file.

Change-Id: Ic535a744e6927698d59006f1971e0efc289cc4ee