Well, it turns out that qemu is required and kvm-qemu-img was the source of the problem. Removing this and installing qemu instead fixed the problem.
Actually I did the other way round: yum remove qemu (which is in the extras repo) yum install -x qemu kvm (excluding qemu and thus kvm-qemu-img will be taken)
My idea was to test the official upstream vendor stuff and only this.