Let Jukebox playlists continue after leaving and rejoining the world.

As of the fourth snapshot of 26.4, leaving and rejoining world or server stops any Jukebox music that was playing, meaning you would have to inconveniently go back to the Jukebox and restart it. This still happens with the new Jukebox playlist feature. 

If the drop is planning to make Jukeboxes used more, then this should be fixed in the same drop.