b5083aff99
45de287447
provides a fix to autodect the backing format.
Until we have that fix in libguestfs, specify it explicitly.
Related: rhbz#1998820
Change-Id: Ibfbefcacd684f046c0798987483c48a97e222092
Signed-off-by: Bogdan Dobrelya <bdobreli@redhat.com>