Policy.json should be defined by user

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

Change-Id: I1d58c632442cd1ffb19f2020ab9e5e63bea975a9
diff --git a/metadata.yml b/metadata.yml
index a16c24e..3a8709d 100644
--- a/metadata.yml
+++ b/metadata.yml
@@ -1,3 +1,6 @@
 name: "cinder"
 version: "2016.4.1"
 source: "https://github.com/salt-formulas/salt-formula-cinder"
+dependencies:
+  - name: keystone
+    source: "https://github.com/salt-formulas/salt-formula-keystone"