pfctl: teach route-to to deal with interfaces with multiple addresses

The route_host parsing code set the interface name, but only for the first
node_host in the list. If that one happened to be the inet6 address and the
rule wanted an inet address it'd get removed by remove_invalid_hosts() later
on, and we'd have no interface name.

We must set the interface name for all node_host entries in the list, not just
the first one.

PR: 223208
MFC after: 2 weeks