Policy.json should be defined by user

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

Change-Id: Ide69691fe5dc4dd684159ad3f29bfeb1638c9bf3
diff --git a/README.rst b/README.rst
index 252f845..cc6f92b 100644
--- a/README.rst
+++ b/README.rst
@@ -132,6 +132,18 @@
           allow_credentials: True
           max_age: 86400
 
+Configuration of policy.json file
+
+.. code-block:: yaml
+
+    nova:
+      controller:
+        ....
+        policy:
+          context_is_admin: 'role:admin or role:administrator'
+          'compute:create': 'rule:admin_or_owner'
+          # Add key without value to remove line from policy.json
+          'compute:create:attach_network':
 
 Compute nodes
 -------------