switch from keystoneclient to keystoneauth

move glanceclient to keystoneauth as keystoneclient's auth session,
plugins and adapter code has been deprecated.

refer to [1] for more information.

1: https://github.com/openstack/python-keystoneclient/commit/1a84e24fa4ce6d3169b59e385f35b2a63f2257f0

implements bp: use-keystoneauth

Co-Authored-By: Itisha <ishadewan07@gmail.com>
Change-Id: I88fb327628e1bec48dc391f50d66b3deab4a8ab9

releasenotes/notes/bp-use-keystoneauth-e12f300e58577b13.yaml

@@ -0,0 +1,11 @@
+---
+prelude: >
+    Switch to using keystoneauth for session and auth plugins.
+other:
+  - >
+    [`bp use-keystoneauth <https://blueprints.launchpad.net/python-glanceclient/+spec/use-keystoneauth>`_]
+    As of keystoneclient 2.2.0, the session and auth plugins code has
+    been deprecated. These modules have been moved to the keystoneauth
+    library. Consumers of the session and plugin modules are encouraged
+    to move to keystoneauth. Note that there should be no change to
+    end users of glanceclient.