fix: create /etc/sysctl.d/ for Flatcar before sysctl tasks run

[njuettner]

Change description

Flatcar uses a stateless /etc/ model. Its baselayout package only pre-creates a small set of /etc/ directories (tmpfiles.d/baselayout-etc.conf: /etc/profile.d, /etc/vim, /etc/sudoers.d, …) — /etc/sysctl.d/ is not among them and is never pre-created.

The node role's "Set and persist kernel params" task writes to /etc/sysctl.d/99-sysctl.conf (per node defaults for Flatcar) via ansible.posix.sysctl, which calls mkstemp in the parent directory and fails with FileNotFoundError when the directory is missing.

Fix: add a file task in the setup role's flatcar.yml that ensures /etc/sysctl.d/ exists before any sysctl task runs. This mirrors the existing pattern in node/tasks/flatcar.yml for /etc/modprobe.d/, which is created the same way with the inline note "because of the read-only filesystem on Flatcar in /etc". Aligns with Flatcar's documented convention for persistent sysctl overrides: https://www.flatcar.org/docs/latest/setup/customization/other-settings/

• Is this change including a new Provider or a new OS? (y/n) n

Additional context

Failing task excerpt:

TASK [node : Set and persist kernel params]
FileNotFoundError: [Errno 2] No such file or directory:
'/etc/sysctl.d/.ansible_m_sysctl_<hash>.conf'

[k8s-ci-robot]

@njuettner: 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
pull-ova-all	e6ee1fe	link	false	/test pull-ova-all

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[njuettner]

The pull-ova-all failure is unrelated — photon-5 fails at TASK [setup : Perform a tdnf distro-sync] (before any sysctl task runs) with the upstream iptables / alternatives resolution error already tracked in #1989. The other 5 OVA targets pass, and pull-azure-vhds, pull-gcp-all, and pull-lint are green. pull-ova-all is non-required.

cc @AverageMarcus for review.

[drew-viles]

/lgtm

[AverageMarcus]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AverageMarcus

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