Remove a redundant check
Remove a redundant check

reference.WithDefaultTag is already calling reference.IsNameOnly, so we
don't need to guard it on the outside.

jwhonce/skopeo,mikebrow/skopeo,mtrmac/skopeo,projectatomic/skopeo,jwhonce/skopeo,mtrmac/skopeo,mikebrow/skopeo,masters-of-cats/image,containers/image,mtrmac/skopeo,containers/image,projectatomic/skopeo