Fix a missing parenthesis in the LDAP search request

Signed-off-by: Matthieu Patou <mat@matws.net>
Reviewed-by: Volker Lendecke <vl@samba.org>

Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Sun Jun 30 13:34:13 CEST 2013 on sn-devel-104