Add "list versions" test for Keystone

"list versions" is an inportant API to know which versions are
supported on clouds. This patch adds the corresponding test for
Keystone API.

Change-Id: Ic4aaa16ac1c15d2b82e3dc90402a5b30d19bcd4e
diff --git a/releasenotes/notes/add-list-version-to-identity-client-944cb7396088a575.yaml b/releasenotes/notes/add-list-version-to-identity-client-944cb7396088a575.yaml
new file mode 100644
index 0000000..dd66ff5
--- /dev/null
+++ b/releasenotes/notes/add-list-version-to-identity-client-944cb7396088a575.yaml
@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    Add versions_client module for identity service.
+    This new module provides list_versions() method which shows API versions
+    from Identity service.