A kernel with INET6 always has ::1 on lo0, so in the case of
ipv6_enable="NO" the lo0 can have ::1 with no link-local address.
This is a violation of the IPv6 specification. As a workaround for
this situation, fe80::1 is added in rc.d/auto_linklocal when lo0 has
no link-local address. This should not be harmful for IPv4-only users.