Stop doesn't change Mopidy state

[morgoth]

When using "stop" on gmusic song, Mopidy is still in "playing" state.
There is no music, as it somehow stopped playing, but the state is invalid.
I have no such issue when stopping song from local backend.
For the background how I found this issue you can see mopidy/mopidy.js#5

[jodal]

I'm quite confident that this was fixed as a side effect of 7652f25.

[jodal]

To be a bit more verbose: Previously, the GMusicPlaybackProvider.stop() method was overridden. It is no longer changed in any way, and should work identical to stop in any other Mopidy backend.