wsrep.variables failed in buildbot with deadlock on CREATE USER

wsrep.variables                          w1 [ fail ]

        Test ended at 2018-10-30 10:53:07

CURRENT_TEST: wsrep.variables

mysqltest: At line 132: query 'create user test@localhost' failed: 1213: Deadlock found when trying to get lock; try restarting transaction

The result from queries just before the failure was:

< snip >

gcomm://

SHOW STATUS LIKE 'threads_connected';

Variable_name	Value

Threads_connected	1

SHOW STATUS LIKE 'wsrep_thread_count';

Variable_name	Value

wsrep_thread_count	2

SET @wsrep_slave_threads_saved= @@global.wsrep_slave_threads;

SET GLOBAL wsrep_slave_threads= 10;

# Wait for applier threads to get created.

SHOW STATUS LIKE 'threads_connected';

Variable_name	Value

Threads_connected	1

SHOW STATUS LIKE 'wsrep_thread_count';

Variable_name	Value

wsrep_thread_count	11

set wsrep_on=0;

set wsrep_on=1;

create user test@localhost;