Fix config file generation

After commit 4154ce7578, it is no
longer possible to generate heat.conf because
heat.openstack.common.policy was still listed in
config-generator.conf

Change-Id: Ib81e8f3b4b80f51025ccda1173b03f6f65387b62

config-generator.conf

@@ -9,10 +9,10 @@ namespace = heat.engine.clients
 namespace = heat.engine.notification
 namespace = heat.engine.resources
 namespace = heat.openstack.common.eventlet_backdoor
-namespace = heat.openstack.common.policy
 namespace = heat.api.middleware.ssl
 namespace = heat.api.aws.ec2token
 namespace = keystonemiddleware.auth_token
 namespace = oslo.messaging
 namespace = oslo.db
 namespace = oslo.log
+namespace = oslo.policy