Add RBAC tests for cinder os-quota-class-sets API

This patch adds RBAC tests for the cinder os-quota-class-sets API,
which cover the policy action "volume_extension:quota_classes" [0][1].

[0] https://github.com/openstack/cinder/blob/master/cinder/api/contrib/quota_classes.py#L44
[1] https://github.com/openstack/cinder/blob/master/cinder/api/contrib/quota_classes.py#L55

Change-Id: Iba5dc5caf7ed3f1ad344b0d7b2d6c13a9842cf79
diff --git a/releasenotes/notes/add-quota-classes-tests-3e61e671f6e131df.yaml b/releasenotes/notes/add-quota-classes-tests-3e61e671f6e131df.yaml
new file mode 100644
index 0000000..656f6a1
--- /dev/null
+++ b/releasenotes/notes/add-quota-classes-tests-3e61e671f6e131df.yaml
@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Add RBAC tests for cinder os-quota-class-sets API, which cover the
+    policy action "volume_extension:quota_classes".