vfs_fruit: Don't expect a pathref fsp in unlinkat

vfs_fruit: Don't expect a pathref fsp in unlinkat

The unix syscall unlinkat does not expect a file descriptor for the
to-be-removed object. SMB_VFS_UNLINKAT should also not expect
that. Put the special case into vfs_fruit.

This is required to simplify delete_all_streams next, which should not
have to do an openat_pathref_fsp() on all streams just for the
vfs_fruit case.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>