generic/401: fix test in case of no filetype support

generic/401: fix test in case of no filetype support

Xu Huan reported that this test fails on nfs in some setup.
Apparently, the assumptions made about xfs/ext* do not hold
for nfs.

Relax the verification of filetype not supported case to
allow either DT_UNKNOWN or actual file type on all files and
not only on special dir entires "." and "..".

Convert the unknown d_type replacement code from awk to bash
so it is a bit more readable and flexible.

Reported-by: Xu Huan <xuhuan.fnst@cn.fujitsu.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Tested-by: Xu Huan <xuhuan.fnst@cn.fujitsu.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>