MDEV-13603 Sporadic failure in innodb.dml_purge

In the test, SET GLOBAL innodb_purge_rseg_truncate_frequency = 1
in order to ensure that everything is purged in the slow shutdown.

This could be viewed as a flaw of the slow shutdown.

mysql-test/suite/innodb/r/dml_purge.result

@@ -2,6 +2,7 @@
 # MDEV-12288 Reset DB_TRX_ID when the history is removed,
 # to speed up MVCC
 #
+SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
 CREATE TABLE t1(a INT PRIMARY KEY, b INT NOT NULL)
 ROW_FORMAT=REDUNDANT ENGINE=InnoDB;
 INSERT INTO t1 VALUES(1,2),(3,4);

mysql-test/suite/innodb/t/dml_purge.test

@@ -9,6 +9,8 @@ let MYSQLD_DATADIR=`select @@datadir`;
 --echo # to speed up MVCC
 --echo #
 
+SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
+
 CREATE TABLE t1(a INT PRIMARY KEY, b INT NOT NULL)
 ROW_FORMAT=REDUNDANT ENGINE=InnoDB;
 INSERT INTO t1 VALUES(1,2),(3,4);