Avoid shutdown timeout in innodb.undo_truncate

Let us explicitly wait for purge before invoking a slow shutdown,
so that instrumented builds (such as ASAN or UBSAN) will not
exceed the 60-second timeout during shutdown.

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

@@ -31,5 +31,7 @@ connection con2;
 commit;
 disconnect con2;
 connection default;
+SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
+SET GLOBAL innodb_max_purge_lag_wait=0;
 set global innodb_fast_shutdown=0;
 drop table t1, t2;

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

@@ -45,6 +45,8 @@ connection default;
 let $trx_before= `SHOW ENGINE INNODB STATUS`;
 let $trx_before= `select substr('$trx_before',9)+2`;
 
+SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
+SET GLOBAL innodb_max_purge_lag_wait=0;
 set global innodb_fast_shutdown=0;
 --source include/restart_mysqld.inc
 --replace_regex /.*Trx id counter ([0-9]+).*/\1/