Change the default @@optimizer_switch settings:

- semijoin=on
- firstmatch=on
- loosescan=on

mysql-test/t/subselect_innodb.test

@@ -1,5 +1,7 @@
 -- source include/have_innodb.inc
 
+# Note: the tests uses only non-semijoin subqueries so semi-join switch
+#       settings are not relevant.
 set @subselect_innodb_tmp=@@optimizer_switch;
 set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
 --disable_warnings