Make innodb_ext_key test stable: use innodb_stable_estimates.inc

@@ -314,7 +314,7 @@
 select straight_join * from t0, part ignore index (primary)
 where p_partkey=t0.a and p_size=1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	5	Using where
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	part	eq_ref	i_p_size	i_p_size	9	const,dbt3_s001.t0.a	1

mysql-test/main/innodb_ext_key.test

@@ -5,6 +5,8 @@
 --source include/innodb_prefix_index_cluster_optimization.inc
 --source include/no_valgrind_without_big.inc
 
+--source include/innodb_stable_estimates.inc
+
 SET SESSION DEFAULT_STORAGE_ENGINE='InnoDB';
 
 set @innodb_stats_persistent_save= @@innodb_stats_persistent;