Additional volume v2 backup RBAC tests

Add additional RBAC tests to ``VolumesBackupsRbacTest``, providing
coverage for the following policy action:

  * volume_extension:backup_admin_actions:reset_status

Change-Id: Id5d1539a3721fed3d16cf3aa1bb826f7832b6924
diff --git a/releasenotes/notes/more-volume-backup-tests-c3f10aa245df2a4b.yaml b/releasenotes/notes/more-volume-backup-tests-c3f10aa245df2a4b.yaml
new file mode 100644
index 0000000..8d71130
--- /dev/null
+++ b/releasenotes/notes/more-volume-backup-tests-c3f10aa245df2a4b.yaml
@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Add additional RBAC tests to ``VolumesBackupsRbacTest``, providing coverage
+    for "volume_extension:backup_admin_actions:reset_status".