[PATCH v2] xfstests: improve test 286 for repeated unwritten/hole extents.

[Mark Tinguely]

Enlarge the test coverage of 286 to includes file mapping with repeated
hole/unwritten/unwritten_without_data/data intersections.

Those two new sub-tests could help verifying the current seek_data/seek_hole
improvements.

Signed-off-by: Jie Liu <jeff.liu at oracle.com>
Reviewed-by: Mark Tinguely <tinguely at sgi.com>
Reviewed-by: Christoph Hellwig <hch at lst.de>


Committed to git://oss.sgi.com/xfs/cmds/xfstests.git, master branch.

--Mark.