Revert "default enable AllowAdditionalPlayers"

This reverts commit 308f3369e41cfee1662d83aa7d64c8a40e0f8ab4.

this is a BAAAD idea to enable, i will commit a variable
rename because it doesn't do what one espects:
currently it allows _anyone_ to connect to the host, regardless of script password
verification, as result spoofing player names become possible again and the server
cannot prevent people from joining anymore by changing their passwords and people can
even snatch existing player slots by connecting faster than them