smbd: Decouple grant_fsp_oplock_type from oplock validation

smbd: Decouple grant_fsp_oplock_type from oplock validation

This makes grant_fsp_oplock_type independent from the values computed
in validate_oplock_types. It *might* make oplock calculation a bit
slower for heavily shared files, as we are walking the share mode array
twice. But we are doing so much stuff in open that I doubt the difference
is measurable. It clears up the code for me however, and I think that's
worth it.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Michael Adam <obnox@samba.org>