OKD-239: Consolidate OpenStack and PowerVS hostname handling into mco-hostname script

[Prashanth684]

Manual cherry-pick of #4866 needed for OKD

[Prashanth684]

/cc @mdbooth @EmilienM

[EmilienM]

/lgtm

[mdbooth]

/lgtm

@Prashanth684 but to be clear:

• OCP 4.18's RHCOS image doesn't contain the SELinux policy regression and doesn't require this fix, but it will work fine. OCP 4.18 does not need Allow afterburn to mount and read config drives fedora-selinux/selinux-policy#2584 because it doesn't contain the regression that it fixes.
• IIUC OKD 4.18's OS image does have the SELinux policy regression. Fixing it requires BOTH this fix AND Allow afterburn to mount and read config drives fedora-selinux/selinux-policy#2584 in the OS image

For OCP: backporting this fix is neutral. It will work fine with or without this change.

For OKD: backporting THIS FIX ALONE will allow OpenStack workers to retrieve metadata from the metadata service over a link local address. This covers the majority of OpenStack users. To retrieve metadata from a config drive also requires fedora-selinux/selinux-policy#2584. This covers the remaining minority of OpenStack users, but all PowerVS users.

[Prashanth684]

/lgtm

@Prashanth684 but to be clear:

• OCP 4.18's RHCOS image doesn't contain the SELinux policy regression and doesn't require this fix, but it will work fine. OCP 4.18 does not need Allow afterburn to mount and read config drives fedora-selinux/selinux-policy#2584 because it doesn't contain the regression that it fixes.
• IIUC OKD 4.18's OS image does have the SELinux policy regression. Fixing it requires BOTH this fix AND Allow afterburn to mount and read config drives fedora-selinux/selinux-policy#2584 in the OS image

For OCP: backporting this fix is neutral. It will work fine with or without this change.

For OKD: backporting THIS FIX ALONE will allow OpenStack workers to retrieve metadata from the metadata service over a link local address. This covers the majority of OpenStack users. To retrieve metadata from a config drive also requires fedora-selinux/selinux-policy#2584. This covers the remaining minority of OpenStack users, but all PowerVS users.

Thanks for the clarity @mdbooth .

For OKD: backporting THIS FIX ALONE will allow OpenStack workers to retrieve metadata from the metadata service over a link local address. This covers the majority of OpenStack users

This is the case that has me backporting the fix to 4.18. I believe the selinux-policy fix is already present in Centos, i will need to verify, but i think we can live with that limitation till 4.19.

[Prashanth684]

/retest

[openshift-ci-robot]

@Prashanth684: This pull request references OKD-239 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the bug to target the "4.18.z" version, but no target version was set.

In response to this:

Manual cherry-pick of #4866 needed for OKD

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[openshift-ci]

@Prashanth684: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/e2e-azure-ovn-upgrade-out-of-change	19a888b	link	false	/test e2e-azure-ovn-upgrade-out-of-change
ci/prow/e2e-gcp-op-techpreview	19a888b	link	false	/test e2e-gcp-op-techpreview
ci/prow/e2e-vsphere-ovn-upi-zones	19a888b	link	false	/test e2e-vsphere-ovn-upi-zones

Full PR test history. Your PR dashboard.

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[pablintino]

The change looks good to me
(I do not have approve/review permissions)

[djoshy]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: djoshy, EmilienM, mdbooth, Prashanth684

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[ptalgulk01]

/label cherry-pick-approved