smb3: Do not send SMB3 SET_INFO if nothing changed

An earlier commit had a typo which prevented the
optimization from working:

commit 18dd8e1a ("Do not send SMB3 SET_INFO request if nothing is changing")

Thank you to Metze for noticing this.  Also clear a
reserved field in the FILE_BASIC_INFO struct we send
that should be zero (all the other fields in that
struct were set or cleared explicitly already in
cifs_set_file_info).

Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org> # 4.9.x+
Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>