main.innodb_mysql_lock fails sporadically in buildbot

CURRENT_TEST: main.innodb_mysql_lock

mysqltest: At line 51: query 'INSERT INTO t1 VALUES (2)' succeeded - should have failed with errno 1213...

The result from queries just before the failure was:

#

# Bug #22876 Four-way deadlock

#

DROP TABLE IF EXISTS t1;

# Connection 1

set @@autocommit=0;

CREATE TABLE t1(s1 INT UNIQUE) ENGINE=innodb;

INSERT INTO t1 VALUES (1);

# Connection 2

set @@autocommit=0;

INSERT INTO t1 VALUES (2);

INSERT INTO t1 VALUES (1);

# Connection 3

set @@autocommit=0;

DROP TABLE t1;

# Connection 1

# Connection 1 is now holding the lock.

# Issuing insert from connection 1 while connection 2&3 

# is waiting for the lock should give a deadlock error.

INSERT INTO t1 VALUES (2);