s3: cldap: cldap_multi_netlogon_send() fails with one bad IPv6 address.

s3: cldap: cldap_multi_netlogon_send() fails with one bad IPv6 address.

Analysis by: Rebecca Gellman <rebecca@starfleet-net.co.uk>

Ignore cldap_socket_init() failure when sending
multiple cldap netlogon requests. Allow cldap_netlogon_send()
to catch the bad address and correctly return through a
tevent subreq.

Make sure cldap_search_send() copes with cldap parameter == NULL.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12381

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Tue Oct 18 02:16:20 CEST 2016 on sn-devel-144