Fix functorch/test/test_control_flow (#85981)
The tests weren't being run in PyTorch CI. On deeper investigation, it
looks like the test file doesn't work under the unittest test runner (it
works under pytest though).
This PR enables running these tests under unittest and also marks things
that now fail as expected failure. We should fix these at some point.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85981
Approved by: https://github.com/samdow, https://github.com/voznesenskym
