Log checkpoint saves at start and finish

[lepan-google]

Log checkpoint saves at start and finish

[github-actions]

beep boop 🤖: 🙏 The following files have warnings. In case you are familiar with these, please try helping us to improve the code base.

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Your code was analyzed with PyLint. The following annotations have been identified:

************* Module nemo.lightning.pytorch.callbacks.model_checkpoint
nemo/lightning/pytorch/callbacks/model_checkpoint.py:643:0: C0301: Line too long (146/119) (line-too-long)
nemo/lightning/pytorch/callbacks/model_checkpoint.py:111:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/pytorch/callbacks/model_checkpoint.py:174:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/pytorch/callbacks/model_checkpoint.py:251:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/pytorch/callbacks/model_checkpoint.py:258:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/pytorch/callbacks/model_checkpoint.py:262:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/pytorch/callbacks/model_checkpoint.py:275:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/lightning/pytorch/callbacks/model_checkpoint.py:22:0: W0611: Unused import lightning.pytorch (unused-import)

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Your code has been rated at 9.77/10

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Mitigation guide:

• Add sensible and useful docstrings to functions and methods
• For trivial methods like getter/setters, consider adding # pylint: disable=C0116 inside the function itself
• To disable multiple functions/methods at once, put a # pylint: disable=C0116 before the first and a # pylint: enable=C0116 after the last.

By applying these rules, we reduce the occurance of this message in future.

Thank you for improving NeMo's documentation!

[akoumpa]

Hi @lepan-google,

thanks for the PR, can you fix DCO and push again?

DCO instructions:

Ensure you have a local copy of your branch by [checking out the pull request locally via command line](https://help.github.com/en/github/collaborating-with-issues-and-pull-requests/checking-out-pull-requests-locally).
In your local branch, run: git rebase HEAD~2 --signoff
Force push your changes to overwrite the branch: git push --force-with-lease origin lepan-nemo```