xfs/629: single extent files should be within tolerance

xfs/629: single extent files should be within tolerance

The test passes if we have between 2 and 40 extents (despite what
the comment says!), with the target being 20. There is absolutely no
reason for considering a single extent file a failure - that
indicates the filesystem completely defeated the fragmentation
behaviour the test was trying to cause.  Hence expand the range of
"test pass" tolerance to 1-41 extents.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Zorro lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>