s3:winbind: BUG 9386: Failover if netlogon pipe is not available.

s3:winbind: BUG 9386: Failover if netlogon pipe is not available.

Samba continues to query a broken DC while the DC did not finish to
rebuild Sysvol (after a Windows crash, for example). It causes end users
to received strange codes while trying to authenticate, even if there is
a secondary DC available.

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Mon Nov 12 18:57:18 CET 2012 on sn-devel-104