MDEV-12233 main.mysql_upgrade_noengine fails in buildbot on ppc64le

verify that tests don't leave mysql_upgrade_info in datadir

mysql-test/t/plugin_auth.test

@@ -522,6 +522,8 @@ SELECT IS_NULLABLE, COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS
   WHERE TABLE_SCHEMA= 'mysql' AND TABLE_NAME= 'user' AND
     COLUMN_NAME IN ('plugin', 'authentication_string')
   ORDER BY COLUMN_NAME;
+let $datadir= `select @@datadir`;
+remove_file $datadir/mysql_upgrade_info;
 
 
 --echo #