Refactor tests in pytorch's test/dist_autograd_test.py file (#31803)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31803
Refactored the following fairly similar functions:
1. `test_context_cleanup_tensor_with_grad`
2. `test_context_cleanup_tensor_no_grad`
3. `test_context_cleanup_no_tensors`
by creating a helper function `context_cleanup_test_helper` that can be invoked with the appropriate arguments.
Test Plan: Verified by running tests.
Differential Revision: D19269246
fbshipit-source-id: bfb42b078ad56b97ceeecf0d68b4169768c2c453
