SPORADICALLY ON WEEKLY/DAILY 5.6/5.7

Problem:
=======
In test case 4, while waiting for slave threads to go down
an error condition is reached and stop_slave.inc fails with
following error.

included from ./include/stop_slave.inc at line 84:
At line 142: Error condition reached in
include/wait_for_slave_param.inc

Analysis:
========
Prior to test case 4 master's UUID file is temporarily
replaced with slave's UUID file to test some error
scenarios.  Once all these tests are done master's original
UUID file is restored and the master server is restarted.

As part of test case 4 START SLAVE IO_THREAD is invoked and
an assert is added which verifies that slave is still
referring to master's original UUID.

Upon successful test stop_slave_io.inc is called to stop both
threads.

On slow platforms the START SLAVE IO_THREAD tries to connect
to master server before the master server is ready for
connections.

Test failure debug log shows like this:-
======================================
**** ERROR: Last_IO_Errno = '2013' while waiting for slave
parameter Slave_IO_Running = No ****
DO_NOT_CHECK_IN_THIS_LINE: include/show_rpl_debug_info.inc
should only be used for debugging. Never check in a test
that calls it on success.  CURRENT_CONNECTION = 'slave'

############################## slave ######################

**** SHOW WARNINGS on slave ****
SHOW WARNINGS;
Level   Code    Message

**** SELECT replication-related variables on slave ****
SELECT NOW(), @@SERVER_ID, @@SERVER_UUID, @@PORT;
NOW()   2018-07-13 07:41:54

Slave gave up at 07:41:54

Last_IO_Errno   2013
Last_IO_Error   error connecting to master
'root@127.0.0.1:13050' - retry-time: 1  retries: 1

Master server's error log shows:-
===============================
2018-07-13 07:41:54 32093 [Note] Event Scheduler: Loaded 0
events
2018-07-13 07:41:54 32093 [Note]
/export/home/pb2/test/sb_2-29588355-1531456600.5/mysql/usr/
sbin/mysqld-debug: ready for connections.

IO thread tried to connect master just before master server
was up and it got an error 2013. "stop_slave.inc" was
invoked before the IO thread retried and hence test fails.

Fix:
===
Replaced START SLAVE IO_THREAD with start_slave_io.inc.