Use oslo module for policy configuration

Change-Id: I14eca815d87d94278abdba5294bb427a9fe14e31

manifests/policy.pp

@@ -36,4 +36,6 @@ class mistral::policy (
 
   create_resources('openstacklib::policy::base', $policies)
 
+  oslo::policy { 'mistral_config': policy_file => $policy_path }
+
 }

spec/classes/mistral_policy_spec.rb

@@ -20,6 +20,7 @@ describe 'mistral::policy' do
         :key   => 'context_is_admin',
         :value => 'foo:bar'
       })
+      is_expected.to contain_mistral_config('oslo_policy/policy_file').with_value('/etc/mistral/policy.json')
     end
   end