xfstests generic 308: test write to the last block of max file size on ext4

xfstests generic 308: test write to the last block of max file size on ext4

On unpatched ext4 if an extent exists which includes the block right
before the maximum file offset, and the block for the maximum file
offset is written, the kernel panics.

On patched ext4, the write would get EFBIG since we lower s_maxbytes
by one fs block.

Regression test for commit:
f17722f ext4: Fix max file size and logical block counting of extent format file

Though it's an ext4 specific issue, it's no harm to run on all file
systems, so put it in generic.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Rich Johnston <rjohnston@sgi.com>
[rjohnston@sgi.com renumbered test to next in group sequence]
Signed-off-by: Rich Johnston <rjohnston@sgi.com>