Enforce ID and roles in top

Adapt to current private pillar top:
- match ID grain for inclusion of ID files
- check for role existence

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

pillar/top.sls

@@ -4,9 +4,13 @@
 {{ saltenv }}:
   '*':
     - common
-  '{{ id }}':
+  'id:{{ id }}':
+    - match: grain
     - ignore_missing: True
     - id.{{ id.replace('.', '_') }}
-  {%- for role in roles %}
+{%- if roles | length > 0 %}
+  '{{ id }}':
+  {% for role in roles %}
     - role.{{ role }}
   {%- endfor %}
+{%- endif %}