bootstrap: Ignore podman warning for deprecation of cgroups v1

What this PR does / why we need it:

Both the control plane cluster and workloads cluster are running with cgroups v1.

Since Podman v5, warning messages have started to appear in jobs logs[1]

Add environment variable to ignore these warnings and reduce noise in job logs.

[1] https://prow.ci.kubevirt.io/view/gs/kubevirt-prow/pr-logs/pull/kubevirt_kubevirt/12196/pull-kubevirt-e2e-k8s-1.29-sig-compute/1805168405502758912#1:build-log.txt%3A323

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #

Special notes for your reviewer: /cc @dhiller @xpivarc

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR. Approvers are expected to review this list.

[ ] Design: A design document was considered and is present (link) or not required
[ ] PR: The PR description is expressive enough and will help future contributors
[ ] Code: Write code that humans can understand and Keep it simple
[ ] Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
[ ] Upgrade: Impact of this change on upgrade flows was considered and addressed if required
[ ] Testing: New code requires new unit tests. New features and bug fixes require at least on e2e test
[ ] Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature / API change.
[ ] Community: Announcement to kubevirt-dev was considered

Release note:

kubevirt / project-infra

bootstrap: Ignore podman warning for deprecation of cgroups v1 #3485