TF: add test for `PushToHubCallback`
# What does this PR do?

Adds a test to TF's `PushToHubCallback`
_The documentation is not available anymore as the PR was closed or merged._<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20231). All of your documentation changes will be reflected on that endpoint.<|||||>Could you ensure it works with `huggingface_hub` version `v0.11.0rc1`? I think there was an issue with this callback.

cc @Wauplin <|||||>To be more precise, it should already work with `v0.11.0rc1` (was not the case with `v0.11.0rc0`) BUT a warning message should be triggered "Creating a repository through 'clone_from' is deprecated". To prevent this warning, `PushToHubCallback` should create the repo before cloning it. Something like:
```py
create_repo(repo_id, exists_ok=True)

repo = Repository(clone_from=repo_id)
```<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20231). All of your documentation changes will be reflected on that endpoint.<|||||>All tests are now passing with `HUGGINGFACE_CO_STAGING=1 py.test tests/test_modeling_tf_common.py::TFModelPushToHubTester -vv`, tested against version `0.10.1` of the hub.

@Wauplin I've factored in the `create_repo()` before cloning the repo 👍 

@Rocketknight1 it was indeed failing because of the lack of `compile()`. After the fix, I ran against a problem where the last epoch was not being stored (because of the process kill). Let me know if you agree with the changes in `PushToHubCallback`<|||||>Nice, thanks for making the change @gante !