vfs_fruit: avoid dereferencing fsp->base_fsp in fruit_fstat_meta_stream()

vfs_fruit: avoid dereferencing fsp->base_fsp in fruit_fstat_meta_stream()

This helps avoiding a NULL dereference on systems where additional
patches modify the following condition in open_file()

  if ((open_access_mask & (FILE_READ_DATA|FILE_WRITE_DATA|FILE_APPEND_DATA|FILE_EXECUTE)) ||
      (!file_existed && (local_flags & O_CREAT)) ||
      ((local_flags & O_TRUNC) == O_TRUNC) ) {

to

  if ((open_access_mask & (FILE_READ_DATA|FILE_WRITE_DATA|FILE_APPEND_DATA|FILE_EXECUTE|DELETE_ACCESS)) ||
      (!file_existed && (local_flags & O_CREAT)) ||
      ((local_flags & O_TRUNC) == O_TRUNC) ) {

Ie addtionally check open_access_mask against DELETE_ACCESS. As a result
opens with DELETE_ACCESS go through the code that does an fd_open() plus
a subsequent fstat().

That will trigger a crash in fruit_fstat_meta_stream() when a client
wants to delete a file for deletion. When we open base file for delete,
we call open_streams_for_delete() which internally calls create-file
with NTCREATEX_OPTIONS_PRIVATE_STREAM_DELETE which prevents opening of
the base_fsp. Voila, combined with the change described above you get a
NULL deref.

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sun Dec  2 07:52:34 CET 2018 on sn-devel-144