./mtr --mysqld=--default-storage-engine=maria --mem --skip-ndb temp_table truncate --force
The root cause of the problem has been reported as BUG#30309
"mysql_truncate() does not inform engine that the recreated table is temporary"
The temporary fix used here is that when mysql_truncate() identifies
a temp table of engine "Maria" it declares it non-transactional,
thus the table is re-created by ha_maria::create() as non-transactional.


sql/mysqld.cc:
  porting fix of BUG#29133 (mysqld takes too much time to shutdown
  without this fix, I can't wait for the next merge)
sql/sql_delete.cc:
  a hack to work around BUG#30309 "mysql_truncate() does not inform
  engine that the recreated table is temporary"