FreeBSD 12.x workaround for IPv6 ifconfig is needed on 12.4 as well

FreeBSD 12.x workaround for IPv6 ifconfig is needed on 12.4 as well

Commit 16d7f2cd4d90 tried to remove an FreeBSD 12.x ifconfig inet6
workaround based on the understanding that the upstream fix for
bug 248172 went into 12.4, but that was a misread of the code - 12.4
needs the workaround as well, fixed in 13.0.

Also extend comment to point to /etc/network.subr, which is the real
source of the problematic code

        if checkyesno ipv6_activate_all_interfaces; then
                _ipv6_opts="-ifdisabled"
        elif [ "$1" != "lo0" ]; then                   <<<<
                _ipv6_opts="ifdisabled"                <<<<
        fi

Trac: 1226

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20230306080744.66069-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26335.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>