vtkThalliumRunLoop: avoid busy waiting for tasks
vtkThalliumRunLoop was using default scheduler which caused the run loop to use a busy wait. This was causing the CPU to be pegged to 100 even when no work was being done. Fixed that.
vtkThalliumRunLoop was using default scheduler which caused the run loop to use a busy wait. This was causing the CPU to be pegged to 100 even when no work was being done. Fixed that.