Use keystoneauth instead of keystoneclient

keystoneauth was split out last cycle as a library specifically to deal
with doing auth functions so that people who do not need to do keystone
CRUD operations can just consume only the auth session parts. As part
of modernizing keystone interactions, use keystoneauth instead of
keystoneclient.

Change-Id: Ieae0773ebbb8655ed79d496dd393482e2792e404

requirements.txt

@@ -9,6 +9,7 @@ greenlet>=0.3.2
 iso8601>=0.1.9
 Jinja2>=2.8 # BSD License (3 clause)
 jsonschema!=2.5.0,<3.0.0,>=2.0.0
+keystoneauth1>=2.1.0
 keystonemiddleware!=2.4.0,>=2.0.0
 netaddr!=0.7.16,>=0.7.12
 oslo.config>=2.7.0 # Apache-2.0