/kind bug

Description

podman load on xz compressed files fails.

Steps to reproduce the issue:

1. Perform a podman load on an xz compressed file.

Describe the results you received:
open container-feeder471485113/manifest.json: not a directory

There are two things related to this issue. The first one is that the fall-through logic in PullImage is masking the actual bug, which made debugging the issue harder. I guess we could improve the situation by being more verbose when falling through the various transports. The second one is that containers/image currently doesn't support xz compressed images and compressed layers. @cyphar has fixed the latter with containers/image#427. I tested containers/image#427 locally with libpod by updating the vendored image library, which required just a minor tweak in the code to reflect the new tar API.

Describe the results you expected:
A successful image load.