netinet: do not broadcast PRC_REDIRECT_HOST on ICMP redirect

This is expensive and useless call. It has been useless since Alexander
melifaro@ moved the forwarding table to nexthops with passive invalidation.
What happens now is that cached route in a inpcb would get invalidated
on next ip_output().

These were the last users of pfctlinput(), so garbage collect it.

Reviewed by: melifaro
Differential revision: https://reviews.freebsd.org/D36156