initscripts 1.0: checkroot.sh: Stop doing random positive login regarding fsck.

initscripts 1.0: checkroot.sh: Stop doing random positive login regarding fsck.
* It's ok to do negative logic, for example limit scope of operation if we know
we can't do it (ex.: we don't support fscking something else but ext2/ext3,
so we have to ignore user's request to do fsck on other fstype).
* But it's not ok to do fsck if user didn't request it, or moreover if he
requested *not* to do it.