Updated openstack/openstack
Project: openstack/python-openstackclient  1d9194d4cba7dd5d7211bea2a408cdf0faf249e4

Put pbr and six first in requirements list

Each of them have scenarios where it's important that they install
first.

Change-Id: Ia9fff6e94651693f9fa74ca676771b19144bcd8b