Only notify userland about resolved ARP entries if the Ethernet address changed or if we asked for it.
Only notify userland about resolved ARP entries if the Ethernet address
changed or if we asked for it.

Should reduce the RTM_RESOLVE storm seeing by claudio@

With inputs from and ok mikeb@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars