This regression was introduced in MDEV-16515.
We would fail to drop a temporary table on client disconnect,
because trx_is_interrupted() would hold. To add insult to
injury, in MariaDB 10.1, InnoDB temporary tables are actually
persistent, so the garbage temporary tables will never be dropped.

row_drop_table_for_mysql(): If several iterations of
buf_LRU_drop_page_hash_for_tablespace() are needed,
do not interrupt dropping a temporary table even after
the transaction was marked as killed.

Server shutdown will still terminate the loop, and also DROP TABLE
of persistent tables will keep checking if the execution was aborted.