Handle UFS/FFS file deletion from cylinder groups with check-hash failure.

When a file is deleted, its blocks need to be put back in the free
block list and its inode needs to be put back in the inode free list.
These lists reside in cylinder-group maps. If either some of its blocks
or its inode reside in a cylinder-group map with a bad check hash
it is not possible to free the associated resource. Since the cylinder
group cannot be repaired until the filesystem is unmounted these
resources cannot be freed. They simply accumulate in memory. And
any attempt to unmount the filesystem loops forever trying to flush them.

With this change, the resource update claims to succeed so that the
file deletion can successfully complete. The filesystem is marked as
requiring an fsck so that before the next time that the filesystem is
mounted, the offending cylinder groups are reconstructed causing the
lost resources to be reclaimed.

A better solution would be to downgrade the filesystem to read-only,
but that capability is not currently implemented.

Reported-by: Peter Holm
Tested-by: Peter Holm
MFC-after: 1 week
Sponsored-by: The FreeBSD Foundation