Fix that music delivery is not always resumed

When playback is paused by play_token_lost (e.g. another client on the
same account started playing), and then resumed, music delivery will not
continue. Therefore, the music will play as long as the buffer lasts,
and then go silent until you change track. This commit makes music
delivery continue after resume.
Merge pull request #19 from trygveaa/fix/resume-music-delivery

Fix that music delivery is not always resumed