Nettoie les entrées qui restent lors du redémarrage de slon

declare
        v_row           record;
begin
        for v_row in select nl_nodeid, nl_conncnt, nl_backendpid
                        from sl_nodelock
                        for update
        loop
                if killBackend(v_row.nl_backendpid, 'NULL') < 0 then
                        raise notice 'Slony-I: cleanup stale sl_nodelock entry for pid=%',
                                        v_row.nl_backendpid;
                        delete from sl_nodelock where
                                        nl_nodeid = v_row.nl_nodeid and
                                        nl_conncnt = v_row.nl_conncnt;
                end if;
        end loop;

        return 0;
end;