FIX make sure we import the correct object from multiprocessing (#53282)
Fixes #44687.
The issue was that the Process object is not the one from the `_default_context` which should be `loky` when nesting `loky` calls.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53282
Approved by: https://github.com/VitalyFedyunin
