Should clean the memory usage of MemTracker when a hashJoin query ends

[wshwsh12]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

conn-1:

        drop table if exists t;
        create table t (a int);
        drop table if exists ta;
        create table ta (b int);
        insert into t values (1);
        insert into ta values (11);
        drop table if exists session_info;
        create table session_info(id int, connection_id int);
        insert into session_info values (1, 1);
        select * from t, ta;


conn-2:
        select * from information_schema.processlist where command='Sleep';

2. What did you expect to see? (Required)

tidb> select * from information_schema.processlist where command='Sleep';
+-----+------+-----------------+------+---------+------+------------+------+------------------------------------------------------------------+------+------+----------+
| ID  | USER | HOST            | DB   | COMMAND | TIME | STATE      | INFO | DIGEST                                                           | MEM  | DISK | TxnStart |
+-----+------+-----------------+------+---------+------+------------+------+------------------------------------------------------------------+------+------+----------+
| 403 | root | 127.0.0.1:51398 | test | Sleep   |    3 | autocommit | NULL | f6d4ca2ed2b282163cf06ad3a1c36996c1d2ebc999f4ac453057a8de6acd7f96 |    0 |    0 |          |
+-----+------+-----------------+------+---------+------+------------+------+------------------------------------------------------------------+------+------+----------+
1 row in set (0.00 sec)

3. What did you see instead (Required)

tidb> select * from information_schema.processlist where command='Sleep';
+-----+------+-----------------+------+---------+------+------------+------+------------------------------------------------------------------+------+------+----------+
| ID  | USER | HOST            | DB   | COMMAND | TIME | STATE      | INFO | DIGEST                                                           | MEM  | DISK | TxnStart |
+-----+------+-----------------+------+---------+------+------------+------+------------------------------------------------------------------+------+------+----------+
| 403 | root | 127.0.0.1:49459 | test | Sleep   |    3 | autocommit | NULL | f6d4ca2ed2b282163cf06ad3a1c36996c1d2ebc999f4ac453057a8de6acd7f96 | 1176 |    0 |          |
+-----+------+-----------------+------+---------+------+------------+------+------------------------------------------------------------------+------+------+----------+

4. What is your TiDB version? (Required)

Only master
introduced by d63a5fd