Policy.json should be defined by user

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

Change-Id: I1accd9557cc241a55d5e898b9350b34e078b82a6
diff --git a/tests/pillar/server_plugin_dirs.sls b/tests/pillar/server_plugin_dirs.sls
index 846bab0..087df91 100644
--- a/tests/pillar/server_plugin_dirs.sls
+++ b/tests/pillar/server_plugin_dirs.sls
@@ -52,3 +52,7 @@
       plugins:
       - /test/dir1
       - /test/dir2
+    policy:
+      deny_stack_user: 'not role:heat_stack_user'
+      'cloudformation:ValidateTemplate': 'rule:deny_stack_user'
+      'cloudformation:DescribeStackResource':