kubernetes/preinstall: dns vars cleanup

- Move validation from facts to verify-settings
- Move set_fact to vars/

roles/kubernetes/preinstall/vars/main.yml

@@ -90,3 +90,5 @@ dhclient_supersede:
   domain-name-servers: "{{ ([nameservers, cloud_resolver] | flatten | unique) if dns_early else nameserverentries }}"
   domain-name: "{{ [dns_domain] }}"
   domain-search: "{{ default_searchdomains + searchdomains }}"
+configured_nameservers: "{{ (resolvconf_slurp.content | b64decode | regex_findall('^nameserver\\s*(\\S*)', multiline=True) | ansible.utils.ipaddr)
+                            if resolvconf_stat.stat.exists else [] }}"