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/metadata.yml b/metadata.yml
index 7445fbd..0ee34f0 100644
--- a/metadata.yml
+++ b/metadata.yml
@@ -1,3 +1,6 @@
 name: "nova"
 version: "2017.2"
 source: "https://github.com/openstack/salt-formula-nova"
+dependencies:
+  - name: keystone
+    source: "https://github.com/salt-formulas/salt-formula-keystone"