MDEV-29934 rpl.rpl_start_alter_chain_basic, rpl.rpl_start_alter_restart_slave sometimes fail in BB with result content mismatch

rpl.rpl_start_alter_chain_basic was used to fail sporadically due
to a missed GTID master-slave synchronization which was necessary
because of the following SELECT from GTID-state table.

Fixed with arranging two synchronization pieces for two
chain slaves requiring that.

Note rpl.rpl_start_alter_restart_slave must have been fixed by
MDEV-30460 and 87e1372 (manual) merge commit.

Author: andrelkin

mysql-test/suite/rpl/r/rpl_start_alter_chain_basic.result

@@ -64,7 +64,10 @@ connection server_2;
 select domain_id, seq_no from mysql.gtid_slave_pos order by seq_no desc limit 1;
 domain_id	seq_no
 0	12
+connection server_1;
+include/save_master_gtid.inc
 connection server_3;
+include/sync_with_master_gtid.inc
 select domain_id, seq_no from mysql.gtid_slave_pos order by seq_no desc limit 1;
 domain_id	seq_no
 0	12
@@ -77,6 +80,7 @@ select @@slave_parallel_threads;
 @@slave_parallel_threads
 0
 connection server_4;
+include/sync_with_master_gtid.inc
 select domain_id, seq_no from mysql.gtid_slave_pos order by seq_no desc limit 1;
 domain_id	seq_no
 0	12

mysql-test/suite/rpl/t/rpl_start_alter_chain_basic.test

@@ -39,7 +39,11 @@ connect(slave_node,127.0.0.1,root,,test, $SERVER_MYPORT_2);
 --connection server_2
 select domain_id, seq_no from mysql.gtid_slave_pos order by seq_no desc limit 1;
 
+--connection server_1
+--source include/save_master_gtid.inc
 --connection server_3
+--source include/sync_with_master_gtid.inc
+
 select domain_id, seq_no from mysql.gtid_slave_pos order by seq_no desc limit 1;
 --source include/stop_slave.inc
 --eval set global slave_parallel_threads = $slave_parallel_threads;
@@ -49,6 +53,7 @@ select domain_id, seq_no from mysql.gtid_slave_pos order by seq_no desc limit 1;
 select @@slave_parallel_threads;
 
 --connection server_4
+--source include/sync_with_master_gtid.inc
 select domain_id, seq_no from mysql.gtid_slave_pos order by seq_no desc limit 1;
 
 --source include/rpl_end.inc