fsck: tests: add test for repairing invalid filename

The exfat specification stipulates 41 invalid file name
characters. In invalid_name/exfat.img.tar.xz, 41 files were
created with these invalid file name characters.

Signed-off-by: Yuezhang Mo <[email protected]>
Reviewed-by: Aoyama Wataru <[email protected]>