Refactor and improve the front-end logic of radio title fetching
Refactor and improve the front-end logic of radio title fetching

Functionally, the problem was that during longer periods of listening
the Internet radio, the application got confused and could start
fetching the radio info multiple times in a row every ~30s. There were
at least two root causes behind this:
1. At least HLS streaming seems to randomly fire extra 'play' events
  although the playing is already ongoing. Hence, binding the radio
  info fetching to this event caused surprises.
2. The app could cancel the scheduled radio info update but not such
  operation which had already started.

paulijar/music,owncloud/music,owncloud/music,owncloud/music,owncloud/music,paulijar/music,paulijar/music,paulijar/music,owncloud/music,paulijar/music