tests/upgrade: Handle container case

[cgwalters]

upgrade: Remove old tar code

We can rely on the OS being a container now.

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Port to use rpmostree-client-go

This is a general cleanup, but a specific motivation here
is we were missing the container-image-reference field which I
want to use later.

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Rename GetRpmOstreeStatusJSON -> GetRpmOstreeStatus

Because the fact that it was JSON is irrelevant to the caller.

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tests/upgrade: Handle container case

We switched rawhide to default to a container image reference;
adapt the code to handle this case. We skip all the zincati
stuff here and just directly rebase.

Closes: coreos/fedora-coreos-tracker#1614

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[dustymabe]

Looks mostly good to me. It shouldn't affect that path, but maybe let's hold this until Tuesday to let our triple release builds go through smooth.

[cgwalters]

{err=error: failed to read input object (not a Template?): resource mapping not found for name: "clean-up" namespace: "" from "/var/lib/jenkins/jobs/coreos-assembler/branches/PR-3659/workspace/process17175549336496222947.markup": no matches for kind "Template" in version "v1"
ensure CRDs are installed first

No idea what's going on there, something in Jenkins just fell over looks like.