Support Keystone versionless endpoints
Support Keystone versionless endpoints

Uses keystone.client instead of keystone.client.v3 with session and auth
to return a keystone client with the discovered URL.

Also sets project_domain_name and user_domain_name do "Default" as they
are expected by Keystone.

Change-Id: I8fce922e2907584138a132f37887f227eabe9abe
Partial-Bug: #1688320

openstack/openstack-ansible-plugins,os-cloud/openstack-ansible-plugins,os-cloud/openstack-ansible-plugins,openstack/openstack-ansible-plugins