xfs_repair: fix max block offset test

xfs_repair: fix max block offset test

Eryu pointed out that in fstest xfs/071, we find corruption
reported at the end.  This test attempts to do IO at the
maximum possible offsets, and repair yields:

inode 1027 - extent offset too large - start 70, count 1, offset 2251799813685247
correcting nextents for inode 1027
bad data fork in inode 1027
would have cleared inode 1027

Repair is complaining that an extent *starts* at the maximum
block, but AFAICT, starting there is just fine, as long as
we also end there.  i.e. a one-block extent at the limit
is just fine.

So change the xfs_repair test to allow this situation.

Also, the warning text is a bit unclear, mixing in the physical
block w/ the logical block... rearrange that a little to make
it obvious.

Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>