sys-apps/systemd: add systemd patch from v252.12

[tormath1]

It fixes an issue with Systemd service restart when the main process is being killed by a SIGHUP signal.

Closes: flatcar/Flatcar#1157
Commit-Ref: systemd/systemd-stable@34e834f

Testing done

• locally tested that the patch applies sudo ebuild systemd-252.11-r1.ebuild prepare
• docker: extend restart test case mantle#447
• Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)
• Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.

$ sudo ./bin/kola run --qemu-image /home/mathieu/flatcar/stable/flatcar_production_qemu_image.img docker.containerd-restart
=== RUN   docker.containerd-restart
--- FAIL: docker.containerd-restart (70.78s)
        cluster.go:117: Unable to find image 'ghcr.io/flatcar/busybox:latest' locally
        cluster.go:117: latest: Pulling from flatcar/busybox
        cluster.go:117: 3f4d90098f5b: Pulling fs layer
        cluster.go:117: 3f4d90098f5b: Verifying Checksum
        cluster.go:117: 3f4d90098f5b: Download complete
        cluster.go:117: 3f4d90098f5b: Pull complete
        cluster.go:117: Digest: sha256:a20bc8249a9e522a11102c61230350537cfa0bc1fef41d382eb660a3bc0b853a
        cluster.go:117: Status: Downloaded newer image for ghcr.io/flatcar/busybox:latest
        docker.go:545: Containerd is not running (could not find pid) after signal: SIGHUP
FAIL, output in _kola_temp/qemu-2023-08-10-1932-113273
harness: test suite failed
$ sudo ./bin/kola run --qemu-image ./flatcar/pr1058/flatcar_production_qemu_uefi_image.img docker.containerd-restart
=== RUN   docker.containerd-restart
--- PASS: docker.containerd-restart (98.99s)
        cluster.go:117: Unable to find image 'ghcr.io/flatcar/busybox:latest' locally
        cluster.go:117: latest: Pulling from flatcar/busybox
        cluster.go:117: 3f4d90098f5b: Pulling fs layer
        cluster.go:117: 3f4d90098f5b: Verifying Checksum
        cluster.go:117: 3f4d90098f5b: Download complete
        cluster.go:117: 3f4d90098f5b: Pull complete
        cluster.go:117: Digest: sha256:a20bc8249a9e522a11102c61230350537cfa0bc1fef41d382eb660a3bc0b853a
        cluster.go:117: Status: Downloaded newer image for ghcr.io/flatcar/busybox:latest
PASS, output in _kola_temp/qemu-2023-08-10-1933-113682

[github-actions]

Build action triggered: https://github.com/flatcar/scripts/actions/runs/5832504748

[jepio]

LGTM - but I agree with deferring to @dongsupark or @krnowak for their opinion on cherry-pick vs. update systmed to v252.13 (in some channels).

[krnowak]

I'm fine with adding a patch - it fixes the issue and does not bring potential regressions that a systemd update could have. We can still update systemd in a separate PR.

[tormath1]

cherry-picked to:

• flatcar-3510
• flatcar-3602
• flatcar-3689