add executor test for scatter partial results
add executor test for scatter partial results

Signed-off-by: Michael Demmer <4b836671cce77b1b2fbe63e5b2a1661879d8af44@slack-corp.com>

mahak/vitess,HubSpot/vitess,enisoc/vitess,dcadevil/vitess,dcadevil/vitess,davygeek/vitess,mahak/vitess,HubSpot/vitess,dcadevil/vitess,mahak/vitess,enisoc/vitess,tinyspeck/vitess,dcadevil/vitess,dcadevil/vitess,enisoc/vitess,enisoc/vitess,davygeek/vitess,vitessio/vitess,tinyspeck/vitess,tinyspeck/vitess,dcadevil/vitess,mahak/vitess,enisoc/vitess,vitessio/vitess,dcadevil/vitess,tinyspeck/vitess,mahak/vitess,enisoc/vitess,vitessio/vitess,enisoc/vitess,davygeek/vitess,davygeek/vitess,tinyspeck/vitess,HubSpot/vitess,davygeek/vitess,davygeek/vitess,davygeek/vitess,mahak/vitess,mahak/vitess,HubSpot/vitess,vitessio/vitess,HubSpot/vitess,HubSpot/vitess,vitessio/vitess,HubSpot/vitess,vitessio/vitess,tinyspeck/vitess,HubSpot/vitess,tinyspeck/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess