Making openstack domain name optional

roles/kubernetes/preinstall/templates/openstack-cloud-config.j2

@@ -4,4 +4,6 @@ username={{ openstack_username }}
 password={{ openstack_password }}
 region={{ openstack_region }}
 tenant-id={{ openstack_tenant_id }}
+{% if openstack_domain_name is defined and openstack_domain_name != "" %}
 domain-name={{ openstack_domain_name }}
+{% endif %}