Use minikube in Ubuntu based tests

[kashifest]

Recently we have seen that CentOS E2Es are failing in different tests since the CI infra shift. In contrast, ubuntu e2es are rather stable. CentOS failures are mostly causing problems and main branch PRs which are left hanging for unrelated issues. There are few steps which we can perform the phase out CentOS tests for the time being:

• Use minikube in Ubuntu to make sure ironic is deployed as k8s deployment instead of local containers as it is now. This is the fundamental difference currently between Ubuntu and CentOS tests - Make minikube the default ephemeral cluster #1404
• Phase out CentOS tests as required from prow in project-infra repo as well github branch protection settings.
• Bring back CentOS (if deemed necessary) once the CI infra has better hardware and tests are not flaky. CentOS periodics which are not being phased out can signal this.

[kashifest]

/triage accepted

[metal3-io-bot]

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/lifecycle stale

[Rozzii]

/remove-lifecycle stale

[Rozzii]

@Sunnatillo @kashifest my memory is fogy about this wasn't there more progress on this one?

[metal3-io-bot]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
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/lifecycle stale

[dtantsur]

/remove-lifecycle stale

Starting Ironic locally will not be compatible with ironic-standalone-operator (unless metal3-io/ironic-standalone-operator#86 is done), so I highly vote for using minikube on Ubuntu as well.

[tuminoid]

I guess the only argument keeping it off minikube is to simulate cases where Ironic is not installed in k8s, which has sometimes revealed some assumptions. This is of course not IRSO compatible, and it does not need to be. I agree with the maintenance burden though, so it should be considered if its worth it or not for the sake of testing.