Fix warning in salt v3003

The 'gid_from_name' argument in the user.present state has been replaced
with 'usergroup'. Update your SLS file to get rid of this warning.

Author: bbinet

linux/system/user.sls

@@ -49,7 +49,7 @@ system_user_{{ name }}:
   {%- if user.gid is defined and user.gid %}
   - gid: {{ user.gid }}
   {%- else %}
-  - gid_from_name: true
+  - usergroup: true
   {%- endif %}
   {%- if user.groups is defined %}
   - groups: {{ user.groups }}