As of now, event scheduler is not started by default in MySQL
server. As part of this worklog, event scheduler will be started
by default in the MySQL server.

Changes done as part of this WL:
1. Enable event scheduler thread :
     event_scheduler system variable is set to ON by default to
     start the event scheduler thread.
     SHOW PROCESSLIST command and information_schema.processlist
     will show an extra entry for the event scheduler now.

2. Fix test cases to execute with the event scheduler ON by:
     - Record result files with the new default behavior.
     - Remove SET command from tests and option from .opt
       file to switch ON event scheduler for event_scheduler
       specific tests. Add condition to make sure that
       event_scheduler is ON for these specific tests.
     - Wait condition in tests depend on output from SHOW
       PROCESSLIST and INFORMATION_SCHEMA.PROCESSLIST. Fix the
       wait conditions to consider event_scheduler.