Fixed heap_btree test to make it repeatable

mysql-test/r/heap_btree.result:
  Make test repeatable
mysql-test/t/heap_btree.test:
  Make test repeatable

mysql-test/r/heap_btree.result

@@ -68,13 +68,16 @@ explain select * from t1 where a in (869751,736494,226312,802616);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	uniq_id	uniq_id	4	NULL	4	where used; Using index
 drop table t1;
-create table t1 (x int not null, y int not null, key x  using BTREE (x), unique y  using BTREE (y))
+create table t1 (x int not null, y int not null, key x  using BTREE (x,y), unique y  using BTREE (y))
 type=heap;
 insert into t1 values (1,1),(2,2),(1,3),(2,4),(2,5),(2,6);
+explain select * from t1 where x=1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	x	x	4	const	1	where used
 select * from t1 where x=1;
 x	y
-1	3
 1	1
+1	3
 select * from t1,t1 as t2 where t1.x=t2.y;
 x	y	x	y
 1	1	1	1

mysql-test/t/heap_btree.test

@@ -42,9 +42,10 @@ alter table t1 type=myisam;
 explain select * from t1 where a in (869751,736494,226312,802616);
 drop table t1;
 
-create table t1 (x int not null, y int not null, key x  using BTREE (x), unique y  using BTREE (y))
+create table t1 (x int not null, y int not null, key x  using BTREE (x,y), unique y  using BTREE (y))
 type=heap;
 insert into t1 values (1,1),(2,2),(1,3),(2,4),(2,5),(2,6);
+explain select * from t1 where x=1;
 select * from t1 where x=1;
 select * from t1,t1 as t2 where t1.x=t2.y;
 explain select * from t1,t1 as t2 where t1.x=t2.y;