It turns out that our suites don't exercise fsync, at least not very much
(I couldn't find it in all the places I looked for it). This tester
was written by Ted T'so and updated by Chris Mason; I just made it
work on a smaller dataset (256MB) because 8GB against a small cluster takes
more time than we want to wait.
Signed-off-by: Greg Farnum <greg@inktank.com>
