MDEV-23709 : Galera test failure on galera_fk_cascade_delete_debug

Add wait_condition so that inserts to parent and child are replicated
and applied before we set debug sync point.

mysql-test/suite/galera/r/galera_fk_cascade_delete_debug.result

@@ -46,6 +46,7 @@ ON DELETE CASCADE
 ) ENGINE=InnoDB;
 INSERT INTO parent VALUES (1);
 INSERT INTO child VALUES (1,0,1);
+connection node_2;
 connect node_1a, 127.0.0.1, root, , test, $NODE_MYPORT_1;
 SET GLOBAL debug_dbug = "d,sync.wsrep_apply_cb";
 connection node_2;

mysql-test/suite/galera/t/galera_fk_cascade_delete_debug.test

@@ -61,20 +61,21 @@ CREATE TABLE child (
 INSERT INTO parent VALUES (1);
 INSERT INTO child VALUES (1,0,1);
 
+--connection node_2
+--let $wait_condition = SELECT COUNT(*) = 1 FROM child;
+--source include/wait_condition.inc
+
 # block applier before applying
 --connect node_1a, 127.0.0.1, root, , test, $NODE_MYPORT_1
 SET GLOBAL debug_dbug = "d,sync.wsrep_apply_cb";
 
 --connection node_2
---let $wait_condition = SELECT COUNT(*) = 1 FROM child;
---source include/wait_condition.inc
 DELETE FROM parent;
 
 --connection node_1a
 # wait until applier has reached the sync point
 SET SESSION DEBUG_SYNC = "now WAIT_FOR sync.wsrep_apply_cb_reached";
 
-
 --connection node_1
 # issue conflicting write to child table, it should fail in certification
 --error ER_LOCK_DEADLOCK