Vanishing client playlists: Improve handling of client playlists for synchronized players

[rsplaul]

I keep loosing the current client playlist of synchronized player groups when I restart the server. Instead an old or empty playlist is applied to the player group.

A few tests – although I didn’t check the actual code – indicate, that this has to do with the handling of playlists when players are synchronized:

When players B and C are synchronized to player A, the original clientplaylist_<mac_of_player_B>.m3u and clientplaylist_<mac_of_player_C>.m3u files in the prefs folder are retained for whatever reason. After a server restart it can happen, that any of those two files (and not clientplaylist_<mac_of_player_A>.m3u) is used as the playlist for the player group. I suppose it depends on the order, in which the players are recognized by the server – so it gets even worse, when a bigger number of players is synchronized to a player group.

My suggestion would be to overwrite the clientplaylist_<mac_of_player>.m3u files at the time, the respective player is synchronized to another player. There is no reason to retain the old playlist, since there is no way to restore it anyways.