'Reactivate image.
For a full list of available parameters, please refer to the official
API reference:
http://developer.openstack.org/api-ref/image/v2/#reactivate-image'

def reactivate_image(self, image_id):

    url = ('images/%s/actions/reactivate' % image_id)
    (resp, body) = self.post(url, None)
    self.expected_success(204, resp.status)
    return rest_client.ResponseBody(resp, body)
