update writer factory to ignore writers that don't work without MPI for vtkADIOSWriter
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
The vtkADIOS{Reader,Writer} require MPI so adding in mpi_required to their XML proxy definitions. Also, adding in a check in vtkSMWriterFactory if the writer requires MPI and it's not initialized on the session that is doing the writing.