Description of problem:

The dosfslabel tool returns error code 1, even if it was successful.

The code is currently:

    return fs_close(rw) ? 1 : 0;

where fs_close returns 1 if something was written, and 0 else.

This test could be inverted as writing means success, but reading the
code I don't think it can fail anyway as neither write_label or fs_write
does any check so I think it could probably just always return 0.