Fix bug #58, fails to invalidate query cache.
Fix bug #58, fails to invalidate query cache.

CREATE TABLE t1(i INTEGER);
CREATE TABLE t2(i INTEGER);
SELECT * FROM t1;
BEGIN;
DELETE FROM t2 WHERE i = 0;
INSERT INTO t1(i) VALUES(1);
COMMIT;

SELECT * FROM t1;

At commit pgpool tries to delete cache for t2 but failes because
there's no oid table entry for t2. Problem is, it fails to check oid
table for t1. So cahce for t1 remains and the last SELECT incorrectly
returns cached data. Fix is, continuing to check oid table entries.

treasure-data/prestogres,treasure-data/prestogres,treasure-data/prestogres,treasure-data/prestogres,treasure-data/prestogres,treasure-data/prestogres,treasure-data/prestogres