As a step towards using keystoneauth instead of keystoneclient, remove
the deprecated to-be-removed-in-mitaka neutron auth options so that we
don't have to translate the deprecated code paths to the new library
interface.
bp: keystoneclient-to-keystoneauth
Co-Authored-By: Morgan Fainberg <morgan.fainberg@gmail.com>
Change-Id: I3e3393d99533a70379822178983f73d5eef09bee