smbd: Focus smb_file_link_information on correct posix'ness

smbd: Focus smb_file_link_information on correct posix'ness

In the SMB1 unix extensions, posix'ness is a property of the SMB
request, because it's tied to the connection. In the upcoming SMB3
extensions, this will become a property of the file name, it's being
set at SMB2_CREATE time. To correctly transfer posix'ness of the
filename to the destination name, we can't look at the
req->posix_pathnames here, the SMB2_SETINFO call has not set
that. This is still correct for SMB1, as the per-connection posix'ness
has spilled into the filename there too.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Tue Mar 19 18:46:28 UTC 2019 on sn-devel-144