During following a symbolic link we received err_buf from SMB2_open().
While the validity of SMB2 error response is checked previously
in smb2_check_message() a symbolic link payload is not checked at all.
Fix it by adding such checks.

Cc: Dan Carpenter <dan.carpenter@oracle.com>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: NPavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: NSteve French <smfrench@gmail.com>