MDEV-34568 rpl.rpl_mdev12179 - correct for Windows

Simplify in an attempt to avoid:

mysqltest: At line 275: File already exist: on the write_file
lines.

Using write_line as that's what a lot of other tests
do for writing small bits to a expect file.

Review thanks Valdislav Vaintroub

mysql-test/suite/rpl/t/rpl_mdev12179.test

@@ -55,9 +55,7 @@ SET sql_log_bin=1;
 # Restart the slave mysqld server, and verify that the GTID position is
 # read correctly from the new mysql.gtid_slave_pos_innodb table.
 
---write_file $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
-wait
-EOF
+--write_line wait $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
 --shutdown_server
 --source include/wait_until_disconnected.inc
 
@@ -94,9 +92,7 @@ DROP TABLE mysql.gtid_slave_pos;
 RENAME TABLE mysql.gtid_slave_pos_innodb TO mysql.gtid_slave_pos;
 SET sql_log_bin=1;
 
---write_file $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
-wait
-EOF
+--write_line wait $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
 --shutdown_server
 --source include/wait_until_disconnected.inc
 
@@ -132,9 +128,7 @@ SET sql_log_bin=0;
 ALTER TABLE mysql.gtid_slave_pos ENGINE=Aria;
 SET sql_log_bin=1;
 
---write_file $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
-wait
-EOF
+--write_line wait $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
 --shutdown_server
 --source include/wait_until_disconnected.inc
 
@@ -176,9 +170,7 @@ INSERT INTO mysql.gtid_slave_pos SELECT * FROM mysql.gtid_slave_pos_InnoDB;
 DROP TABLE mysql.gtid_slave_pos_InnoDB;
 SET sql_log_bin=1;
 
---write_file $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
-wait
-EOF
+--write_line "wait" $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
 --shutdown_server
 --source include/wait_until_disconnected.inc
 
@@ -272,9 +264,7 @@ while (!$done)
 # MDEV-15373 engine gtid_slave_pos table name disobeys lower-case-table-names
 # This snippet verifies that engine gtid_slave_pos table is found,
 # its data are up-to-date.
---write_file $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
-wait
-EOF
+--write_line wait $MYSQLTEST_VARDIR/tmp/mysqld.2.expect
 --connection server_2
 --shutdown_server
 --source include/wait_until_disconnected.inc