problem installing CentOS 6/7 on softraid using FAI

[Kevin B]

Hello,

There was a same issue reported back in 2014 
https://lists.uni-koeln.de/pipermail/linux-fai/2014-August/010691.html, 
however, it is still present in the actual versions.

I did some debugging (added `set -xv` in 40-install-grub) and here are 
shell.log's:
Installing Centos 6 - http://paste.debian.net/1085380/
installing Centos 7 - http://paste.debian.net/1085382/

That 'ERROR: Found Software RAID, but the mdadm package was not 
installed' is suggesting mdadm is not installed, but I've purposely 
added mdadm to package_config/CENTOS (in 'PACKAGES yumi' section)
Also, I've double-checked if it was installed in /target and it was.

Here are my disk_config/CENTOS, package_config/CENTOS, 
scripts/CENTOS/40-install-grub - http://paste.debian.net/1085381/

Worth mentioning again that there is no problem at all installing Centos 
6 or 7 without softraid.

Could anyone point me how to get this fixed?