Condense resolvconf sources before starting loop

roles/kubernetes/preinstall/tasks/resolvconf.yml

@@ -28,9 +28,8 @@
     backup: yes
     follow: yes
   with_nested:
-    - "{{ [resolvconffile] + [base|default('')] + [head|default('')] }}"
+    - "{{ [resolvconffile, base|default(''), head|default('')] | difference(['']) }}"
     - [ 'search ', 'nameserver ', 'domain ', 'options ' ]
-  when: item[0] != ""
   notify: Preinstall | restart network
 
 - name: Remove search/domain/nameserver options after block
@@ -41,9 +40,8 @@
     backup: yes
     follow: yes
   with_nested:
-    - "{{ [resolvconffile] + [base|default('')] + [head|default('')] }}"
+    - "{{ [resolvconffile, base|default(''), head|default('')] | difference(['']) }}"
     - [ 'search ', 'nameserver ', 'domain ', 'options ' ]
-  when: item[0] != ""
   notify: Preinstall | restart network