Add designate dashboard to horizon/server/plugin and add defaults

Related: PROD-31956

Change-Id: Ibb0a83c57c79f5097eb7f3953596ce5de7789224
diff --git a/designate/server/cluster/default.yml b/designate/server/cluster/default.yml
index cd0bc1d..9656bc9 100644
--- a/designate/server/cluster/default.yml
+++ b/designate/server/cluster/default.yml
@@ -26,6 +26,7 @@
       domain_id: ${_param:designate_domain_id}
       version: ${_param:designate_version}
       role: ${_param:openstack_node_role}
+      export_policy_grains: ${_param:designate_export_policy_grains}
       admin_api:
         enabled: ${_param:designate_admin_api_enabled}
         enabled_extensions_admin: quotas