core: let kernel add IPv6LL address when method=ignore (rh #1132938)

The IPv6LL address handling in userspace patches failed to handle the
case where the IPv6 method was 'ignore'.  Previously the kernel would
usually add the IPv6LL address itself, but if NM has turned off kernel
IPv6LL then obviously this wouldn't happen.  So when the method is
'ignore', turn off userspace IPv6LL handling and bounce disable_ipv6
to make the kernel add the IPv6LL address if it wants to.
tui: fix incorrect chain up to parent