kaggle_api_extended.py clobbering kaggle.json with environment keys

https://github.com/Kaggle/kaggle-api/blob/master/kaggle/api/kaggle_api_extended.py#L159

This is clobbering any kaggle.json we alter with a newly generated key after expirying it. Those environment variables are being set somewhere (not in public git repo) and are dififcult to find and remove, especially on the kaggle cloud docker.

This is likely a root source of frustration on https://github.com/Kaggle/kaggle-api/issues/46

The workaround to uninstall / reinstall works, but is likely one users will only discover after significant effort.