This option will create an optionally compressed tarball containing a
disk image. This format is used by Google's Compute Engine.
This also adds a new option, tar_disk_name, to set the name of the disk
image that will be wrapped in the final tarball. opts.image_name
continues to be the final output file name.
(cherry picked from commit c941b82b0c)
Related: rhbz#1689140