Code review comment for lp:~alfonsosanchezbeato/media-hub/get-selected-streams

Comments addressed. @Jim, yes, for the moment this is it until we modify media-hub's DBus interface so we can transmit more information to the client like:

* Available tracks with type and description
* Information on which tracks can be played and which not due to missing codecs
* A way to select the tracks to play
* An intermediate state in which we can access to this information but we are still not playing (gstreamer state for the stream would be "paused"). Maybe we can move to that state when media is set instead of moving from the initial gstreamer state to playing when the DBus play() method is invoked.