Before simply not filling-in game length setting resulted in it being
treated as a custom game length (custom game setting). Not it defaults
to a most common used game length - long game with 10 waves. Every other
unrecognized value is still being treated as a custom game.
Previously game dissivulty was switching through a crutch, when we
could've just used key-value option inside the server URL. That crutch
was repurposed to switch game length that is actually requires it.