MDEV-7142: main.index_merge_innodb fails sporadically in buildbot

Attempt to stabilize the testcase.

mysql-test/include/index_merge2.inc

@@ -341,6 +341,7 @@ while ($1)
 alter table t1 add index i2(key2);
 alter table t1 add index i3(key3);
 update t1 set key2=key1,key3=key1;
+analyze table t1;
 
 # to test the bug, the following must use "sort_union":
 --replace_column 9 REF

mysql-test/r/index_merge_innodb.result

@@ -311,6 +311,9 @@ set @d=@d*2;
 alter table t1 add index i2(key2);
 alter table t1 add index i3(key3);
 update t1 set key2=key1,key3=key1;
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
 explain select * from t1 where (key3 > 30 and key3<35) or (key2 >32 and key2 < 40);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index_merge	i2,i3	i3,i2	4,4	NULL	REF	Using sort_union(i3,i2); Using where

mysql-test/r/index_merge_myisam.result

@@ -1146,6 +1146,9 @@ set @d=@d*2;
 alter table t1 add index i2(key2);
 alter table t1 add index i3(key3);
 update t1 set key2=key1,key3=key1;
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
 explain select * from t1 where (key3 > 30 and key3<35) or (key2 >32 and key2 < 40);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index_merge	i2,i3	i3,i2	4,4	NULL	REF	Using sort_union(i3,i2); Using where