sporadic test failures with galera.galera_toi_ddl_nonconflicting

The test fails sporadically with:

CURRENT_TEST: galera.galera_toi_ddl_nonconflicting
mysqltest: At line 57: query 'reap' failed: ER_LOCK_DEADLOCK (1213): Deadlock found when trying to get lock; try restarting transaction

The test script has apparent nondeterministic structure:

--connection node_2

--echo # DDL 1

--send ALTER TABLE t1 ADD COLUMN f3 INTEGER; INSERT INTO t1 VALUES (NULL, 10000, 10000);

--connection node_1a

--source include/galera_wait_sync_point.inc

--source include/galera_clear_sync_point.inc

--echo # This will block on acquiring total order isolation

--connection node_1

--echo # DDL 2

--send CREATE UNIQUE INDEX i1 ON t1(f2);

Due to --send used, the order of ALTER... in node_2 and CREATE... in node_1 can be whatever. This should be fixed. Also the logic of the test should be analyzed to find out which scenario the test is enforcing.