Set Designate mdns to listen on both ipv6 and ipv4

If using an ipv6 external network, mdns needs to be listening on
ipv6 so that bind instances outside the tripleo deployment
can pull their zone data.

Change-Id: I93fea9aa35c3c4207b22dc54542f8580e0444e72

deployment/experimental/designate/designate-mdns-container-puppet.yaml

@@ -117,6 +117,9 @@ outputs:
             - designate_workers_zero
             - {}
             - designate::mdns::workers: {get_param: DesignateWorkers}
+          - designate::mdns::listen:
+            - '0.0.0.0:5354'
+            - '[::]:5354'
       service_config_settings:
         mysql:
           designate::db::mysql::password: {get_param: DesignatePassword}