Update regression test to prevent bogus failure

[rafsun42]

Changes:

• The ORDER BY clause is added to a query that was causing row-ordering difference.

• The debug_parallel_query variable is set to 'regress' around a query that may choose parallel worker and therefore, may output a notice from a parallel worker.

  Setting this option will suppress notices from parallel workers and result in a consistent query output regardless of parallel worker being selected or not. Note that, this option also forces a query to choose parallel worker if it is safe.