This commit adds FILEID_INVALID = 0xff in fid_type to
indicate invalid fid_type

It avoids using magic number 255
Signed-off-by: NNamjae Jeon <linkinjeon@gmail.com>
Signed-off-by: NVivek Trivedi <vtrivedi018@gmail.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>