generic/544: fix inode number ordering code

generic/544: fix inode number ordering code

The code that creates files and moves them to low/high inode number
files writes different file contents before doing the move - leading to
non-reproducible results.

Fix this by writing the file contents after moving them to high/low
inode number files.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>