Prevent failure on empty inventory groups

If role-defined groups exist in the inventory but are empty, execution
fails. This patch ensures that the default value is used not only if the
group is missing, but also if it exists and is empty.

Fixes #31.

Author: aeneby

tasks/main.yml

@@ -80,13 +80,13 @@
 - name: Configure /vsmagent/allowed_clients
   tlconfig:
     param: /vsmagent/allowed_clients
-    value: "{{ groups['thinlinc_masters'] | default(['localhost']) | join(' ') }}"
+    value: "{{ groups['thinlinc_masters'] | default(['localhost'], true) | join(' ') }}"
   notify: restart vsmagent
   when: "'thinlinc_agents' in group_names"
 
 - name: Configure list of agent servers
   tlconfig:
     param: /vsmserver/subclusters/Default/agents
-    value: "{{ groups['thinlinc_agents'] | default(['localhost']) | join(' ') }}"
+    value: "{{ groups['thinlinc_agents'] | default(['localhost'], true) | join(' ') }}"
   notify: restart vsmserver
   when: "'thinlinc_masters' in group_names"