Add a basic tool for copying images from one location to another,
optionally adding a name if it's to local storage. Ideally we could use
skopeo for this, but we don't want to build it.
Use it to initially populate the test/testdata/redis-image directory, if
it's not been cleaned out, with a copy of "docker://redis:latest", and
to copy it in to the storage that ocid is using before we start up ocid.
Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
