If there are two bot infos in scripts/bots.txt then each team can
only add two random bots via bot_minplayers or addbot random.
Pick random bot info from least used bot infos instead of only ones
that are used by zero players. That way a random bot can always be
added to the game.
This rarely affected Quake 3 since there is 32 bot infos. It could
easily affect new games though.