Use latest version of python-openstackclient

Some options in openstack client like --or-show are available only
from 1.0.0. Adding this 'requirement' explictly as openstackclient
is not as part of requirements of other projects.

Change-Id: I96a98331ece15da869a3ea7af80d16fab2351329
Merge "Use latest version of python-openstackclient"