Use updated wsgi file for Keystone 9.0.0 release

httpd/keystone.py is already deprecated in Keystone upstream[1] post
9.0.0 release. This change swiches to use keystone-wsgi-admin and
keystone-wsgi-public to match the upstream change.

[1] https://github.com/openstack/keystone/commit/70a42e7a82ddae9be75dba8f063170a1d13ce301

Change-Id: Iac3bb7309fc88c3e62bb2e92a3272545cbf9a778
Closes-Bug: #1579275