if the kernel argument rootflags is set, then dracut will
not parse the rootfs fstab and rootfsck wil not be set.
if the filesystem can be fsck'ed then its unmounted,
and an entry to the local fstab is written, omitting the last
field.
mounting /sysroot using fstab will then fail.
This change makes sure that the filed is always written.
Signed-off-by: Norbert Lange <norbert.lange@andritz.com>