after circumventing https://bugzilla.opensuse.org/show_bug.cgi?id=1139939 , the
system really finishes installing, and tries to reboot. 

However, all that CP does is entering a program interrupt loop. Even when
activating the zipl menu, this is not displayed.

Things that I tried without success:
- manually set the parameters for disk geometry
- got zipl image and initrd from a system that I knew that works
- installed a ext3 only system
- did the identical partition like on a system that works

I always compared zipl -c /boot/zipl/config -V from a working system with the
broken one, and in the end had no differences, still CP would not boot the
system.

Finally, I did the following to boot the system, which worked (but is not a
solution):
- boot from reader for installation
- go into shell and activate my system disk
- select boot installed system 
- select the right entries

After this, the system came up, without using zipl though. It actually seems to
find the correct entries from grub2-emu.
To reproduce, get a current image from
https://build.opensuse.org/package/binaries/openSUSE:Factory:zSystems/000product:openSUSE-dvd5-dvd-s390x/images 
and do a normal system installation. I did my tests with Build574.1.