Problem:
--------
Sporadic failure was because test expects the value of 'Slave_SQL_Running_State'
to be 'Slave has read all relay log; waiting for more updates' without ensuring
if sql thread has applied all events from relaylog.

Fix:
----
Introduced a wait_condition to wait until slave sql_thread has applied all events
from the relaylog before checking the value of 'Slave_SQL_Running_State'.