bgpd: Make sure Link-Local Next Hop capability has its own update-group
We should involve checking received (not only advertised) capability, because
otherwise we put both peers (one with LL capability, another without) into a
single update-group and send 16-bytes NH instead of 16-bytes and 32-bytes
separately.
Fixes: db853cc97eafee8742cd391aaa2b5bc58a6751ae ("bgpd: Implement Link-Local Next Hop capability") Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>