240: only run when the file system block size is larger than the disk sector size

240: only run when the file system block size is larger than the disk sector size

This test really wants to test partial file-system block I/Os.  Thus, if
the device has a 4K sector size, and the file system has a 4K block
size, there's really no point in running the test.  In the attached
patch, I check that the fs block size is larger than the device's
logical block size, which should cover a 4k device block size with a 16k
fs block size.

I verified that the patched test does not run on my 4k sector device
with a 4k file system.  I also verified that it continues to run on a
512 byte logical sector device with a 4k file system block size.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>