ldb-samba: fix a memory leak in ldif_canonicalise_objectCategory()

ldb-samba: fix a memory leak in ldif_canonicalise_objectCategory()

Searches for '(objectCategory=Person)' will leak a ldb_dn structure
on the ldb_context. These searches are typically used by Zarafa.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=10469

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Thu Jul 17 00:51:57 CEST 2014 on sn-devel-104

(cherry picked from commit 8d33cddcb001a5a78aca036161d6223268274211)

Autobuild-User(v4-0-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-0-test): Thu Jul 17 23:07:24 CEST 2014 on sn-devel-104