Is your feature request related to a problem? Please describe.
Currently after a DFK is cleaned up by dfk.cleanup() , it cleans the DFK but not clearing the reference of the DFK. So, we have to call parsl.clear() to remove the loaded dfk to load another new config. And if we try to load a new without parsl.clear(), it raises a error indicating there is already a loaded config.

Try

parsl.load()
parsl.dfk().cleanup()
parsl.load()

Describe the solution you'd like
it would be better if dfk.cleanup() can clear the reference as well, as after dfk.cleanup() we cant load new config as well as pushing new tasks.