Bug in logic to update expiration times on subsequent tracks when no one is listening

[TheLoombot]

There's a bug in the logic I wrote to update expiration times on subsequent tracks when you skip the first track.

Easiest way to reproduce:

1. Add two 1-minute tracks to the playlist
2. Close the app (and make sure no one else is using it)
3. Come back after 3 minutes
4. Expected behavior: When you return to the app, both tracks should have expired and been removed
5. Actual behavior: The first track is expired and removed, but then the subsequent tracks have their expiration times updated and start playing immediately

Basically, the problem is in the playlist service's recalcTimes method. When we do Updating expiration time on new track 0 ... we need to take the original expiration time into account better... if the track's original expiration time has already passed, it should be removed, not updated!

[TheLoombot]

Pretty straightforward fix actually... just ignore expired tracks and don't bother updating their expiration times! See attached commit 9150a8e