Rhel8 support

[neoakris]

Ran some directions as per
#7130

here's what I've done
git clone git@github.com:VibrentHealth/kops.git
cd kops
git remote add upstream https://github.com/kubernetes/kops
git fetch upstream
git merge upstream/master
git push origin
//(our fork's master is now synced with upstream master)

git checkout -b rhel8_support
git cherry-pick f449e61
git cherry-pick 592d7cd
git cherry-pick 05c5af4
git diff master
//(makes it look like only the desired diff is captured)

Created this new PR
Also worth mentioning: I looked into signing the CLA, and to my knowledge, the VibrentHealth organization signed it, and since myself and Cassandra are part of that organization we're good. Let me know if I'm mistaken on that.

[k8s-ci-robot]

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[rifelpet]

/ok-to-test

[justinsb]

This looks great, thanks for rebasing @neoakris .

The switch from ntp to chrony will take place also for rhel7, which I guess is OK - typically we have tried not to change behavior on previous versions, but in this case I think we can just add it to the release notes for whatever version we first cherry-pick this back to!

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: justinsb, neoakris

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[justinsb]

(Also, I have an open PR to move that to code, so I'll likely just update that one to keep rhel7 / centos7 using the ntp package ... unless there is some reason we should actively change rhel7 / centos7?)