[LTP] [PATCH] open: fix directory verification and misleading test description

[Jinseok Kim]

Hi, Hrubis

Thanks for the review.

I checked fstat/:

None of the existing fstat tests actually verify file type bits as you
suggested.

I think the cleanest solution is to introduce a new test `fstat04.c`
that creates different file types (regular, directory, character, etc.)
and explicitly checks `S_ISREG()`, `S_ISDIR()`, `S_ISCHR()` and so on.

How do you think about removing the O_DIRECTORY case from open01.c and
creating a separate fstat test?

Thanks again,
Jinseok.