Policy.json should be defined by user

User can override and add values to policy.json by creating flat
key-value structure under glance:server:policy.

Change-Id: I4db6b17ab1ff925aa20cd3565417a4b35ed4561e
diff --git a/tests/pillar/single_image_cache.sls b/tests/pillar/single_image_cache.sls
index 772dd12..0e1dff8 100644
--- a/tests/pillar/single_image_cache.sls
+++ b/tests/pillar/single_image_cache.sls
@@ -39,3 +39,6 @@
       enable_management: true
       directory: /var/lib/glance/image-cache/
       max_size: 21474836480
+    policy:
+      publicize_image: "role:admin"
+      add_member: