Fix bad usage of six.moves.cStringIO
Fix bad usage of six.moves.cStringIO

TrivialFix
Closes-Bug: #1523802

Change-Id: I1231c47351fb723367e1673f3fb52f20fc5164f0

openstack/kolla-mesos,openstack/kolla-mesos,asalkeld/kolla-mesos,openstack/kolla-mesos