Use feature branch with Ironic aarch64 backports

Author: m-bull

etc/kayobe/stackhpc.yml

@@ -165,7 +165,7 @@ stackhpc_repo_elrepo_9_version: "{{ stackhpc_repo_distribution }}"
 
 # Kolla source repository.
 stackhpc_kolla_source_url: "https://github.com/stackhpc/kolla"
-stackhpc_kolla_source_version: stackhpc/18.6.0.12
+stackhpc_kolla_source_version: stackhpc-ironic-aarch64
 
 # Kolla Ansible source repository.
 stackhpc_kolla_ansible_source_url: "https://github.com/stackhpc/kolla-ansible"