Comment 2 for bug 1810136

according to https://mariadb.com/kb/en/library/upgrading-from-mariadb-101-to-mariadb-102/+comments/2903 it seems like innodb_fast_shutdown=1 should workaround it.
we should also check https://jira.mariadb.org/browse/MDEV-13603 (innodb_fast_shutdown=0 may fail to purge all history).