generic: _test_generic_punch not blocksize clean

generic: _test_generic_punch not blocksize clean

Test 17 of _test_generic_punch uses the filesystem block size to do
a sub-single block punch. The result of this is a files of
different sizes and md5sums when the filesystem block size changes.
However the only difference in file contents if the length of the
file - the zeroed region is always in the same place. Hence we can
use hexdump rather than md5sum to check the output remains
consistent and the hole remains in the correct place despite the
changing block sizes.

Fix up all the golden output for all the tests that use this
function, too.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>