Fix ban mask being ignored on IPv6 addresses

IPv6 bans had no logic that checked against the address mask on it at all. this is crucial on IPv6 because most users have IPv6 privacy extension, which causes the link-local part of the address to be randomized every time a machine connects to a network. without ban masks, ban circumvention is as easy as just disconnecting from the network and reconnecting to get your link-local address changed, which you can imagine would be a moderation nightmare for server hosts.