[cli-ref] Update python-openstackclient to 2.6.0
[cli-ref] Update python-openstackclient to 2.6.0

Change-Id: Ic42f41b0bb06a6dabe85e7ed870cbadbbdf58eb1

AlekhyaMallina-Vedams/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals