[PATCH] xfstests: add another fallocate test to 214

[PATCH] xfstests: add another fallocate test to 214

ext4 had a regression where it double-accounted used blocks
if you fallocated on top of delalloc blocks.  Ted sent a
c program to exploit it (see "fsstress-induced corruption reproduced"
on linux-ext4 on 12/31/2009) and it's trivial to do the same thing
within the xfstests framework using xfs_io.

This also changes the handcrafted xfs_io tests to use the
_require_xfs_io_falloc helper, not sure how that got missed.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>