Updated openstack/openstack
Project: openstack/tempest  690337527ab43b244f38233d56fc038086222672

Correct volume type api schema validation

Volume type in api response body can be None, so add None value to
volume create and list api  schema validation.

Closes-bug: 1341924

Change-Id: I151b407ea2ec871375cbf96f41269fd8a5414a29