param: disable print notify backchannel by default

param: disable print notify backchannel by default

In handling RemoteFindFirstPrinterChangeNotifyEx requests, the spoolss
server can establish a "backchannel" connection to the print client, as
a mechanism for sending print notifications. This behaviour is governed
by the "print notify backchannel" smb.conf parameter.

This change sets "print notify backchannel" to "no" by default, which
sees Samba respond to RemoteFindFirstPrinterChangeNotifyEx requests with
WERR_SERVER_UNAVAILABLE. In recieving such a response, print clients can
fall back to polling for print queue changes.

Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Günther Deschner <gd@samba.org>
Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Mon Oct 14 18:49:41 CEST 2013 on sn-devel-104