Thanks for filing this. The inet6 inclusion should be handled by the same fix for #1033640 (the nameservice abstraction).
About the other problem you hit, did you make changes to the kea-dhcp6 configuration file, or are you getting these errors right after install? I see you have a valid IPv6 address on the system. If you made changes to /etc/kea/kea-dhcp6.conf, would you mind to share them, so I can more easily reproduce the problem?
