Add RBAC test for communitize_image policy

This commit adds an RBAC test for communitize_image
policy, enforced via:

POST /v2/images with attribute visibility = community [0]

[0] https://github.com/openstack/glance/blob/b7c627ef68c303d4c3182c1a41b36185447039a3/doc/source/policies.rst

Change-Id: Icf2f14f8240389b17da4b92f6f0df168746d06b2
diff --git a/releasenotes/notes/communitize-image-rbac-test-bdf1109e58a6c2e0.yaml b/releasenotes/notes/communitize-image-rbac-test-bdf1109e58a6c2e0.yaml
new file mode 100644
index 0000000..200cc58
--- /dev/null
+++ b/releasenotes/notes/communitize-image-rbac-test-bdf1109e58a6c2e0.yaml
@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Add RBAC test for communitizing image, providing coverage for the policy
+    action "communitize_image".