fedora-kata-osbuilder.sh: Get kernel path from /lib/modules
    
    Rather than /boot. The /lib/modules path is stable, the /boot
    path can be different depending on what distro version we are on,
    for example Fedora CoreOS doesn't put kernels in /boot top dir
    
    Signed-off-by: Cole Robinson <crobinso@redhat.com>