Adding support for the enforce_password option.

This will allow users change their passwords after the initial setting in Salt.

pillar.example

   buser:
     fullname: B User
     password: $6$w.............
+    enforce_password: True
     home: /custom/buser
     createhome: True
     manage_vimrc: False

users/init.sls

     {% if 'password' in user -%}
     - password: '{{ user['password'] }}'
     {% endif -%}
+    {% if 'enforce_password' in user -%}
+    - enforce_password: '{{ user['enforce_password'] }}'
+    {% endif -%}
     {% if user.get('system', False) -%}
     - system: True
     {% endif -%}