The logic in vtkPVDataDeliveryManager that would result in deciding
which representation delivered data that the potential to miss
representation that produced empty data under special cases.
This was because vtkPVDataDeliveryManager was depending on data's MTime
which doesn't always change when `vtkPVDataRepresentation::RequestData`
is executed. Fixed that using a more robust
`vtkDemandDrivenPipeline::DataTime` instead.

Also added a test for the same.