kubernetes/preinstall: dns setting cleanup(dhclient, resolvconf)

We use a lot of facts where variables are enough, and format too early,
which prevent reusing the variables in different contexts.

- Moves set_fact variables to the vars directory, remove unnecessary
 intermediate variables, and render them at usage sites to only do logic
 on native Ansible/Jinja lists.
- Use defaults/ rather than default filters for several variables.

roles/kubernetes/preinstall/tasks/0063-networkmanager-dns.yml

@@ -4,11 +4,12 @@
     path: /etc/NetworkManager/conf.d/dns.conf
     section: global-dns-domain-*
     option: servers
-    value: "{{ nameserverentries }}"
+    value: "{{ nameserverentries | join(',') }}"
     mode: '0600'
     backup: true
   when:
-    - nameserverentries != "127.0.0.53" or systemd_resolved_enabled.rc != 0
+    - ('127.0.0.53' not in nameserverentries
+       or systemd_resolved_enabled.rc != 0)
   notify: Preinstall | update resolvconf for networkmanager
 
 - name: Set default dns if remove_default_searchdomains is false
@@ -21,7 +22,7 @@
     path: /etc/NetworkManager/conf.d/dns.conf
     section: global-dns
     option: searches
-    value: "{{ (default_searchdomains | default([]) + searchdomains | default([])) | join(',') }}"
+    value: "{{ (default_searchdomains | default([]) + searchdomains) | join(',') }}"
     mode: '0600'
     backup: true
   notify: Preinstall | update resolvconf for networkmanager