Make groups optional again

Allow people to use this role for single machines without defining any
master or agent groups.

Author: CendioOssman

templates/thinlinc-setup.answers.j2

@@ -6,7 +6,7 @@ setup-firewall=yes
 setup-selinux=yes
 setup-web-integration=yes
 setup-apparmor=yes
-{% if ansible_fqdn in groups['thinlinc_masters'] %}
+{% if ('thinlinc_masters' not in group_names) or (ansible_fqdn in groups['thinlinc_masters']) %}
 server-type=master
 {% else %}
 server-type=agent