Ensure that test_quick_select doesn't return more rows than in the table

Other changes:
- In test_quick_select(), assume that if table->used_stats_records is 0
  then the table has 0 rows.
- Fixed prepare_simple_select() to populate table->used_stat_records
- Enusre that set_statistics_for_tables() doesn't cause used_stats_records
  to be 0 when using stat_tables.
- To get blackhole to work with replication, set stats.records to 2 so
  that test_quick_select() doesn't assume the table is empty.

mysql-test/main/stat_tables.result

@@ -412,7 +412,7 @@ EXPLAIN
 SELECT * FROM t1 STRAIGHT_JOIN t2 WHERE name IN ( 'AUS','YEM' ) AND id = 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	const	PRIMARY	PRIMARY	4	const	1	Using index
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	0	Using where
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	1	Using where
 ANALYZE TABLE t2;
 Table	Op	Msg_type	Msg_text
 test.t2	analyze	status	Engine-independent statistics collected