try to improve player networking: let playerchecker do ALL the work for adding/removi...

try to improve player networking: let playerchecker do ALL the work for adding/removing players, and let scores updates JUST set the scores. Scores might come before the player, though, and a PL affected player can still get wrong scores for a short while even if networking is fixed, but well, that's PL.

git-svn-id: svn://svn.icculus.org/nexuiz/trunk@4736 f962a42d-fe04-0410-a3ab-8c8b0445ebaa