Problem: binlog_stm_binlog runs INSERT DELAYED queries, and
then prints the contents of the binlog. Before checking the
contents of the binlog, the test waits until the rows have
appeared in the table. However, this is not enough, since
INSERT DELAYED does not write rows to the binlog at the same
time as it writes them to the table. So there is a race.
Fix: Add a FLUSH TABLES before SHOW BINLOG EVENTS. That
waits until the insert_delayed thread is done.