Problem:
=======
Executing test with following options will result in test failure.

./mtr rpl.kill_race_condition{,,,,,,,,,,} --repeat=10 --par 12 --mem

Fix:
====
Test simulates applier thread kill scenario while applying a row event.  But it
doesn't wait for applier to catch the error stop.

Added :wait_for_slave_sql_error.inc to catch the error.

Test uses START SLAVE as a final step and doesn't wait for both threads to
start.

Added: start_slave.inc