Revert image flattening and clean node images before disconnected tests

[rlobillo]

Summary

• Revert the multi-arch image flattening when mirroring to the internal registry: always use --keep-manifest-list=true instead of --filter-by-os=linux/amd64 for internal registry mirrors.
• Clean images stored in nodes (crictl rmi --prune) before running disconnected tests to avoid stale cached images from previous runs.

More details

The --filter-by-os flag (when using internal registry) was flattening multi-arch manifests into single-arch images when mirroring to the internal registry. This caused issues because the manifest list are needed for running tier2 testsuite. Reverting to --keep-manifest-list=true preserves the original manifest structure for all mirror targets.

Additionally, a cleanup step is added at the beginning of the disconnected CI script to prune container images cached on each node, preventing leftover images from prior runs from interfering with the test.

What this PR does / why we need it

1. Reverts commit a43f8b2: removes the conditional --filter-by-os=linux/amd64 flag for internal registry mirrors and restores --keep-manifest-list=true for all mirror operations.
2. Adds node image cleanup: runs crictl rmi --prune on all nodes before mirroring, ensuring a clean state for disconnected validation tests.

🤖 Generated with Claude Code

[rlobillo]

/retest ci/prow/images

[rlobillo]

/retest pull-ci-openshift-cnv-ocp-virt-validation-checkup-main-images

[rlobillo]

/test images

[rlobillo]

/test images

[rlobillo]

@orenc1 This PR has been successfully tested on openshift/release#79293 (comment) (It has been applied from a gist patch before running the self-validation tool).

It's confirmed then that it is working as expected to fully covered the disconnected scenario on the periodic prow job.

Please review, thank you!

[orenc1]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: orenc1, rlobillo

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[openshift-ci]

@rlobillo: The following test 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/images	a678ed1	link	unknown	/test images

Full PR test history. Your PR dashboard.

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[rlobillo]

/cherry-pick release-4.22

[openshift-cherrypick-robot]

@rlobillo: new pull request created: #85

Details

In response to this:

/cherry-pick release-4.22

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