MDEV-22511 innodb.truncate_foreign failed in buildbot with wrong error code

- Adding lock_wait_timeout value as 1 make sure that truncate table
fails instead of making MDL timeout.

mysql-test/suite/innodb/t/truncate_foreign.test

@@ -37,6 +37,7 @@ send DELETE FROM parent;
 
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR fk';
+SET lock_wait_timeout=1;
 --error ER_LOCK_WAIT_TIMEOUT
 TRUNCATE TABLE child;
 SET DEBUG_SYNC='now SIGNAL go';