MDEV-33423: show_analyze sporadically fails at line 226: 'reap' succeeded...

Fix a race condition in a testcase: it tried to KILL a running SET query.
The query could finish before KILL command killed it, which resulted in:

  query 'reap' succeeded - should have failed with error
  ER_QUERY_INTERRUPTED

Fixed by forcing the query to first block for SHOW ANALYZE and then block
again waiting to be KILLed.

mysql-test/main/show_analyze.result

@@ -207,9 +207,12 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_f
 SET debug_dbug=@old_debug;
 # Try to do SHOW ANALYZE for a query that runs a  SET command:
 #
-set @show_explain_probe_select_id=2;
+create table t2 (a int);
+insert into t2 values (1),(2);
+set @show_explain_probe_select_id=3;
 SET debug_dbug='+d,show_explain_probe_join_exec_start';
-set @foo= (select max(a) from t0 where sin(a) >0);
+set @foo= (select max(a) from t2
+where a + (select max(a) from t0 where t0.a>t2.a) < 10000);
 connection default;
 show analyze for $thr2;
 ERROR HY000: Target is not executing an operation with a query plan
@@ -217,6 +220,7 @@ kill query $thr2;
 connection con1;
 ERROR 70100: Query execution was interrupted
 SET debug_dbug=@old_debug;
+drop table t2;
 #
 # Attempt SHOW ANALYZE for an UPDATE
 #

mysql-test/main/show_analyze.test

@@ -213,9 +213,15 @@ SET debug_dbug=@old_debug;
 
 --echo # Try to do SHOW ANALYZE for a query that runs a  SET command:
 --echo #
-set @show_explain_probe_select_id=2; # <---
+create table t2 (a int);
+insert into t2 values (1),(2);
+set @show_explain_probe_select_id=3; # Stop in the subquery.
 SET debug_dbug='+d,show_explain_probe_join_exec_start';
-send set @foo= (select max(a) from t0 where sin(a) >0);
+# t2 has 2 rows so we will stop in the subquery twice: 
+#  - first one to serve the SHOW ANALYZE request
+#  - second one when waiting to be KILLed.
+send set @foo= (select max(a) from t2
+                 where a + (select max(a) from t0 where t0.a>t2.a) < 10000);
 connection default;
 --source include/wait_condition.inc
 --error ER_TARGET_NOT_EXPLAINABLE
@@ -225,7 +231,7 @@ connection con1;
 --error ER_QUERY_INTERRUPTED
 reap;
 SET debug_dbug=@old_debug;
-
+drop table t2;
 
 --echo #
 --echo # Attempt SHOW ANALYZE for an UPDATE