rarpd clobbered any AF_INET information already configured for a given
interface name, so interfaces with more than one IP address made rarpd
listen only for the last address out of all IP aliases.
I changed this, so that AF_LINK information is always collected first
(to ensure the interface name gets its link-layer address associated),
but while looking for AF_INET addresses, the configuration is cloned
if there has already been one IP address seen for that interface name.
Thus, rarpd now effectively listens on all subnets.
MFC after: 1 week
d7706da39f