When used with the ipa_dyndns_iface option, the dynamic DNS code would
blindly put in any addresses the interface has. I think we should filter
addresses such as multicast, loopback and IPv6 link-local -- they don't
belong to DNS.
Adding Honza to CC list as he's probably got the most experience with
address formats and was solving a similar issue on the server side. Are
there any other I should filter out?