Describe the bug
ThreadBuffer as now coded wraps a DataLoader thus it would be logical for Workflow class to accept a ThreadBuffer as the source of data but it is not allowed.

To Reproduce
Instantiate a Workflow class to which you give a ThreadBuffer wrapped DataLoader as a dataloader.

Expected behavior
Just for the workflow to work as it is with a dataloader.

Additional context
https://github.com/Project-MONAI/MONAI/blob/master/monai/engines/workflow.py#L93