Issue in openstack-client that stops nova being in a common-venv

Install the openstack client libraries with 'pip install .' and
not python setup.py develop. The reason for this is that
python setup.py develop had the side effect of changing the
python path inside the virtualenv causing the problems whereas
pip install . doesn't.

I also want to delete the /opt/stack/python-client git directories
later.

Change-Id: Idc68e85c68f1c423f083e656d65d1654688dc84b
Merge "Issue in openstack-client that stops nova being in a common-venv"