fixes #450
if players already have a scheduled game for a round they cannot set
themselves unavailable anymore.
This only affects the team league directly, as in lonewolf and chess960
you cannot set yourself unavailable for an ongoing round anyway.
Pointed out one thing that I believe is a bug, and a few other minor cleanups that I think are worth doing. Ping me when they're done and I'll review it again.
fixes #450 if players already have a scheduled game for a round they cannot set themselves unavailable anymore. This only affects the team league directly, as in lonewolf and chess960 you cannot set yourself unavailable for an ongoing round anyway.