Support flatcar version >= 3815.2.0

[MichaelEischer]

How to categorize this PR?

/area os
/kind enhancement

What this PR does / why we need it:

Flatcar starting from version 3815.2.0 has removed torcx support and replaced it with systemd-sysext. The main difference form a user perspective is that the containerd binaries have moved from /run/torcx/unpack/docker/bin to /usr/bin .

This PR updates the extension to (still) prefer binaries in /run/torcx/unpack/docker/bin but to also fall back to /usr/bin if the former don't exit. This allows using both Flatcar versions that still use torcx and those that only use systemd-sysext.

Which issue(s) this PR fixes:

Special notes for your reviewer:

I've manually tested the change with flatcar 3760.2.0 and 3815.2.0. (although still using Gardener 1.79)

Release note:

The extension now supports Flatcar >= 3815.2.0

[gardener-robot]

@MichaelEischer Thank you for your contribution.

[gardener-robot-ci-1]

Thank you @MichaelEischer for your contribution. Before I can start building your PR, a member of the organization must set the required label(s) {'reviewed/ok-to-test'}. Once started, you can check the build status in the PR checks section below.

[robinschneider]

@vpnachev @rfranzke Could you have a look at it?

[MrBatschner]

/add reviewed/ok-to-test

[plkokanov]

Thanks for the PR, just a minor suggestion on my side.
You cold also include in the TODO comments which is the last version of flatcar that ships with torcx.

[MichaelEischer]

@plkokanov I've updated the TODO comments as suggested

[plkokanov]

/lgtm

[MichaelEischer]

/approve

[gardener-robot]

@MichaelEischer Command /approve is not known.

[MichaelEischer]

@plkokanov Is there anything left to do here to get this PR merged?

[robinschneider]

@plkokanov Is there anything left to do here to get this PR merged?

Would be great to get this merged and released.

[plkokanov]

@plkokanov Is there anything left to do here to get this PR merged?
Would be great to get this merged and released.

/cc @danielfoehrKn @marwinski if they would also like to have a look

[timebertt]

Looks great, thanks!
/lgtm

I suggest merging this by tomorrow if there is no additional feedback.

[gardener-robot]

@timebertt Command /lgtm is not available to you but only to a Maintainer, Member.