Fix a missed argument from a previous refactor
Fix a missed argument from a previous refactor

Region name support got changed a little while ago, and a call that
should now be a keyword argument style stayed as a positional ... which
means that we lost region name support for clouds with more than one
region. (it treated all of them like the first region)

Change-Id: I666758a775b8fc8e03b7e9ddd3aa494c13505612

openstack/python-openstacksdk,dtroyer/python-openstacksdk,redhat-openstack/os-client-config,stackforge/python-openstacksdk,switch-ch/os-client-config,dtroyer/python-openstacksdk,openstack/os-client-config,openstack/python-openstacksdk,stackforge/python-openstacksdk,dtroyer/os-client-config