Eleven - Fix MusicPlaybackSerivce to show the proper metadata when a

downloaded audio file is playing. A call to notify UI of a change in
the song metada was missing which consequently led to song information
not updating in the audio player UI. The ability to handle download
uri ("content://downloads/*") has been added.

The Jira ticket states that there itself isn't working, but
MediaPlayer was able to handle download uri and playback the audio
file. There was code missing to get audio info in such a case.

https://cyanogen.atlassian.net/browse/MUSIC-4

Change-Id: I2c642c337c42c28ac28237de5a655ee55b5b8d33