templates/resolv.conf.j2 : extend ansible_managed line. check variables before use

Author: mbocquet

templates/resolv.conf.j2

@@ -1,19 +1,19 @@
-# {{ ansible_managed }}
+# {{ ansible_managed }}. role: resolv, template: resolv.conf.j2
 
-{% if resolv_search | length > 0 %}
+{% if resolv_search is defined and resolv_search | length > 0 %}
 search {{ resolv_search|join(' ') }}
 {% endif %}
-{% if resolv_domain != "" %}
+{% if resolv_domain is defined and resolv_domain != "" %}
 domain {{ resolv_domain }}
 {% endif %}
 {% for ns in resolv_nameservers %}
 nameserver {{ ns }}
 {% endfor %}
-{% if resolv_sortlist | length > 0 %}
+{% if resolv_sortlist is defined and resolv_sortlist | length > 0 %}
 {% for sl in resolv_sortlist %}
 sortlist {{ sl }}
 {% endfor %}
 {% endif %}
-{% if resolv_options | length > 0 %}
+{% if resolv_options is defined and resolv_options | length > 0 %}
 options {{ resolv_options|join(' ') }}
 {% endif %}