listen-to clusterIP address

[Mark Andrews]

Use IPv6 and listen-on-v6 { any; };.  The IPv4 socket api doesn't have
the hooks to force the UDP replies from the correct address.  The IPv6
socket api has more functionality.

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org