rhcos: Support channels

[cgwalters]

The code was hardcoded to DefaultChannel; add an environment variable
so people (and CI) can use the other channels.

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[ashcrow]

Changes look good. Waiting for CI to return.

[cgwalters]

Hum, no idea what went wrong there.

/test e2e-aws

[wking]

Why would we have RHCOS channels? I thought we wanted to pull RHCOS from the release image, #1286. I think we want Cincinnati channels, not RHCOS channels.

[wking]

See also discussion in #1168.

[cgwalters]

Why would we have RHCOS channels?

They already exist today, the installer just doesn't make them ergonomic to pull.

I thought we wanted to pull RHCOS from the release image, #1286. I think we want Cincinnati channels, not RHCOS channels.

100% agreed! If we are all in agreement to land 1286 very soon I'm fine closing this. But if 1286 isn't going to go in in the next say day or two I'd like to land this so it's easier for others to test using our existing other streams.

Once this lands it's totally fine to revert it in 1286 when rebasing.

[cgwalters]

/hold

Will rebase once #1407 lands

BTW a related PR is #1168

[wking]

BTW a related PR is #1168

Yup, linked above too ;). And I still think that OPENSHIFT_INSTALL_OS_IMAGE_OVERRIDE is a sufficient knob for the moment, and that we'll want to land #1286 soon and drop OPENSHIFT_INSTALL_OS_IMAGE_OVERRIDE entirely soon, and just have RHCOS overrides happen via release images like operator overrides. If there is additional tooling I can help provide (like this script) to make this more convenient without updating the compiled installer, please let me know.

[cgwalters]

Superceded by #1423