Comment 0 for bug 1526342

As we know, baremetal can not directly consume vm format images such as qcow2 etc, have to convert to raw format, only raw image can be copied to disk, however both raw and qcow2 image is in huge size always, so we can add the zip/gzip raw image format which will have very small size for same image, to have low storage and networking cost with such zip/gzip compressed images.

This is useful for user to reuse the 'backup' disk image in gzip format, which is done by manually or supported by another bp backup-disk-to-image.