Xena: drop downstream Barbican

We are not carrying downstream Barbican patches in Xena.

Author: markgoddard

etc/kayobe/kolla.yml

@@ -111,10 +111,6 @@ kolla_openstack_release: TODO
 #     location: https://github.com/openstack/ironic
 #     reference: master
 kolla_sources:
-  barbican-base:
-    type: git
-    location: "https://github.com/stackhpc/barbican.git"
-    reference: stackhpc/xena
   bifrost-base:
     type: git
     location: "{{ kolla_bifrost_source_url }}"