Don't reset plpgsql nest level at every command end

Don't reset plpgsql nest level at every command end

Clean up code for global exit is forgetting about loops that run
hinted commands multiple times. This leads to pg_hint_plan's failure
to affect after the first execution of the inner commands.
The hint below worked only for the first time.

FOR outer IN EXECUTE 'outer-command' LOOP
  FOR inner IN EXECUTE '/*+ hint */ inner-command' LOOP
    <something>
  END LOOP;
END LOOP;