PMProperty should never call UpdateInformation() or Update() or any such
pipeline calls in Pull(). The reason being that Pull() is only called on
root-node in parallel and if the filter is doing parallel communication in any
of those methods then it will hang!!!

Also vtkPMSourceProxy needed to call UpdateInformation() on all subproxies.
Fixed that. This made the code in vtkPMCompoundSourceProxy::UpdateInformation()
obsolete and hence it was removed.