is-default-class is case sensative so we must return a lowercase string

roles/kubernetes-apps/persistent_volumes/openstack/templates/openstack-storage-class.yml.j2

@@ -5,7 +5,7 @@ apiVersion: storage.k8s.io/v1
 metadata:
   name: "{{ class.name }}"
   annotations:
-    storageclass.kubernetes.io/is-default-class: "{{ class.is_default | default(false) }}"
+    storageclass.kubernetes.io/is-default-class: "{{ class.is_default | default(false) | ternary("true","false") }}"
 provisioner: kubernetes.io/cinder
 parameters:
 {% for key, value in (class.parameters | default({})).items() %}