Add Tests for Groups Volume APIs - Part 4

Generic volume groups support was added to Cinder in the
Newton release:
https://blueprints.launchpad.net/cinder/+spec/generic-volume-group

This is the 4th patch that adds the tempest tests for generic
volume groups APIs in Cinder. It adds tests for the following API:

  * update group

Change-Id: I7cc1b7978f24d6cb0e9b13b9387f000b9ca348b3
Co-Authored-By: Imran Ansari <imran.ansari@hpe.com>
diff --git a/releasenotes/notes/add-update-group-tempest-tests-72f8ec19b2809849.yaml b/releasenotes/notes/add-update-group-tempest-tests-72f8ec19b2809849.yaml
new file mode 100644
index 0000000..23c30af
--- /dev/null
+++ b/releasenotes/notes/add-update-group-tempest-tests-72f8ec19b2809849.yaml
@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    Add update_group to groups_client in the volume service library.