can't find fsck_4.2bsd because there was no fstab file saying what
filesystem type it is looking at so it got the filesystem type from
the disk's label. When that fails admins who haven't been in this
situation before are most likely to try "fsck -t ufs /dev/ad0s1a" because
ufs is the type used in fstab files on working systems but that also fails
complaining it can't find fsck_ufs.
This just sets it up so /stand in the MFS image (/sbin is a symlink
to /stand) includes hard links pointing fsck_4.2bsd and fsck_ufs to
fsck_ffs which is what is present in /sbin on installed systems.
Prodded by: obrien
MFC after: 1 day
284acd0781