Explicitly install systemd in the image.
    
    It seems that systemd is required by anaconda which wants
    to setup the default target. Since dnf dependencies to systemd
    was dropped in [0] we need to install it explicitly.
    
    [0] - https://src.fedoraproject.org/rpms/dnf/c/faa199f16041940b85012fb8456b2fca349b6f9e?branch=master
    Signed-off-by: Clement Verna <cverna@tutanota.com>