[nova][ptg] Summary: Replace python-*client with OpenStack SDK

Blueprint: https://blueprints.launchpad.net/nova/+spec/openstacksdk-in-nova Summary: - Enable use of OpenStack SDK from nova. - Phase out use of python-*client (for * in ironic, glance, cinder, neutron...) eventually removing those deps completely from nova. - SDK capable of using ksa oslo.config options, so no changes necessary in deployments; but deployments can start using clouds.yaml as they choose. Agreement: Do it. Action: Reviewers to look at the blueprint and decide whether a spec is needed. efried .