MDEV-25506 fixup: Wait for TRUNCATE recovery

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

@@ -8,6 +8,10 @@ connection default;
 SET DEBUG_SYNC='now WAIT_FOR c';
 # restart
 disconnect wait;
+SET @save_frequency=@@GLOBAL.innodb_purge_rseg_truncate_frequency;
+SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
+InnoDB		0 transactions not purged
+SET GLOBAL innodb_purge_rseg_truncate_frequency=@save_frequency;
 SELECT COUNT(*) FROM t1;
 COUNT(*)
 0

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

@@ -17,7 +17,13 @@ SET DEBUG_SYNC='now WAIT_FOR c';
 --source include/restart_mysqld.inc
 disconnect wait;
 
+SET @save_frequency=@@GLOBAL.innodb_purge_rseg_truncate_frequency;
+SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
+--source include/wait_all_purged.inc
+SET GLOBAL innodb_purge_rseg_truncate_frequency=@save_frequency;
+
 --replace_result 2 0
 SELECT COUNT(*) FROM t1;
 TRUNCATE TABLE t1;
 DROP TABLE t1;
+