Simplify variant list preparation.
Simplify variant list preparation.

Instead of making a copy of the variant list, just point
the slice into it.  This ends up being as efficient as the
original implementation (if the variant is present in variantOrder).

Should not change behavior.

Signed-off-by: Miloslav Trmač <9c008e38982a5397deb855345fb164f0558459ae@redhat.com>

containers/image,containers/image