'kpod push' doesn't use default transport

[TomSweeneyRedHat]

If you don't specify a transport, kpod push doesn't default to a transport. It probably should default to "docker://" if a transport is not provided. A similar fix was made to Buildah at: containers/buildah#260

In the examples below, "docker://" is not specified as the transport in the first call and kpod push fails. It then completes when specified.

# kpod push --cert-dir /root/auth docker.io/library/alpine:latest dockreg.redhat.com:5000/my-alpine2
error getting destination imageReference for "dockreg.redhat.com:5000/my-alpine2": Invalid image name "dockreg.redhat.com:5000/my-alpine2", unknown transport "dockreg.redhat.com"
[root@localhost tmp]# kpod push --cert-dir /root/auth docker.io/library/alpine:latest docker://dockreg.redhat.com:5000/my-alpine2
Getting image source signatures

[TomSweeneyRedHat]

I can't assign this to myself? Regardless, I'm going to grab it.

[rhatdan]

Assigned.

[TomSweeneyRedHat]

Fixed by #42