* Add RHEL 9.0 to CI.
* Add RHEL 9 specific files.
* Add Ubuntu 22.04 and Fedora 36 to CI.
* Another try.
* Adjust kernel memory tests.
* Add more details.
* RHEL 9 doesn't support setting memory swappiness.
* Fix docker_swarm_service tests.
The 'less' case should always have been changed, but it probably was always skipped
due to a too old Docker SDK for Python or a too old Docker daemon.
* More checks / improve checks.
