Fix incorrect `ldbsearch` invocation

Signed-off-by: Timur I. Bakeyev <timur@iXsystems.com>
Reviewed-by: Uri Simchoni <uri@samba.org>
Reviewed-by: Björn Jacke <bjacke@samba.org>

Autobuild-User(master): Uri Simchoni <uri@samba.org>
Autobuild-Date(master): Mon Feb 19 12:31:38 CET 2018 on sn-devel-144
