'Returns an iterator that caches the contents of an image
while the image contents are read through the supplied
iterator.
:param image_id: Image ID
:param image_checksum: checksum expected to be generated while
iterating over image data
:param image_iter: Iterator that will read image contents'

def get_caching_iter(self, image_id, image_checksum, image_iter):

    if (not self.driver.is_cacheable(image_id)):
        return image_iter
    LOG.debug("Tee'ing    image    '%s'    into    cache", image_id)
    return self.cache_tee_iter(image_id, image_iter, image_checksum)
