[cooker] Create OpenMandriva image with mkosi

i've packaged mkosi[1] a tool for creating legacy-free OS images
This tool builds distribution image that can be easily booted from qemu or

First you need to run dnf install mkosi systemd-container

Here is how the process looks like:
1. build image
mkosi -d openmandriva -r rolling --cache=$(pwd) --force --password=classified
2. run image
systemd-nspawn -bi omv-rolling-img

3. Poweroff system
machinectl poweroff omv-rolling-img

More cool features can be found here[2], and i hope this will help a bit with
testing, and in some future to replace our docker builders with systemd-nspawn

4. Import image
machinectl import-raw omv-rolling-img OMV

5. Run, stop, delete image
machinectl start OMV
machinectl poweroff OMV
machineclt remove OMV

[1] - GitHub - systemd/mkosi: Build Legacy-Free OS Images
[2] - mkosi — A Tool for Generating OS Images