update .functests to run stestr
update .functests to run stestr

Updated .functests script to run similar to how it's defined
in tox.ini

Change-Id: I17df28d8cbe0e10e48b26c2f9737308552ea88db

sohonetlabs/python-swiftclient,openstack/python-swiftclient,openstack/python-swiftclient,sohonetlabs/python-swiftclient