Fix MCD image pull failure with mirrored releases

[honza]

RHCOS 9.6 ships a default /etc/containers/policy.json that requires sigstoreSigned verification for quay.io/openshift-release-dev images. When deploying mirrored non-GA releases (nightly/CI), images are not sigstore-signed. Even though registries.conf redirects pulls to the local mirror, the policy check is evaluated against the original image name (quay.io/...), causing signature verification to fail.

This affects two services during node firstboot:

1. machine-config-daemon-pull.service - the initial MCD image pull
2. machine-config-daemon-firstboot.service - MCD's internal pulls for extensions and OS images

The existing generate_podman_policy_args.sh only applies a permissive --signature-policy for podman < 4.4.1, but current RHCOS ships podman 5.x. The MCO also internally regenerates the restrictive policy.json during MachineConfig rendering, overriding any file-level MachineConfig entries.

Fix by adding a MachineConfig manifest with:

• A systemd dropin on machine-config-daemon-pull.service that forces --signature-policy to use the permissive policy-for-old-podman.json
• A new oneshot service that replaces /etc/containers/policy.json with the permissive version before machine-config-daemon-firstboot runs

Only activated when MIRROR_IMAGES is set and OPENSHIFT_RELEASE_TYPE is not "ga".

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign cybertron for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[openshift-ci]

@honza: 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-metal-ipi-serial-ovn-ipv6	8064430	link	false	/test e2e-metal-ipi-serial-ovn-ipv6
ci/prow/e2e-metal-ipi-ovn-ipv6	8064430	link	true	/test e2e-metal-ipi-ovn-ipv6
ci/prow/e2e-metal-ipi-ovn-dualstack	8064430	link	false	/test e2e-metal-ipi-ovn-dualstack

Full PR test history. Your PR dashboard.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.