Make the IPA installer IPv6 friendly
Notable changes include:
* parse AAAA records in dnsclient
* also ask for AAAA records when verifying FQDN
* do not use functions that are not IPv6 aware - notably socket.gethostbyname()
The complete list of functions was taken from http://www.akkadia.org/drepper/userapi-ipv6.html
section "Interface Checklist"