Comment # 1 on bug 1004941 from Thomas Renninger

Leap 42.1 is dracut based and /etc/sysconfig/kernel is deprecated.
Please use:
force_drivers+=" cache_check"
in a /etc/dracut.conf.d/10-mydracut.conf
and rerun mkinitrd.
Double check with:
lsinitrd /boot/initrd |less
whether the file now gets included.