groups: support `absent` like for users.

Also remove warning for passing unknown arguments on group.absent

users/init.sls

 {% set used_user_files = [] %}
 
 {% for group, setting in salt['pillar.get']('groups', {}).items() %}
-users_group_{{ setting.get('state', "present") }}_{{ group }}:
-  group.{{ setting.get('state', "present") }}:
+{%   if setting.absent is defined and setting.absent or setting.get('state', "present") == 'absent' %}
+users_group_absent_{{ group }}:
+  group.absent:
     - name: {{ group }}
-    {%- if setting.get('gid') %}
-    - gid: {{setting.get('gid')  }}
-    {%- endif %}
+{% else %}
+users_group_present_{{ group }}:
+  group.present:
+    - name: {{ group }}
+    - gid: {{ setting.get('gid') }}
     - system: {{ setting.get('system',"False") }}
+{% endif %}
 {% endfor %}
 
 {%- for name, user in pillar.get('users', {}).items()