Fix undefined object in Python model __copy__ template

[tuanchien]

Implements the recommended fix for issue #10856, a Python client bug in the mustache template that causes model copies to fail due to trying to return an undefined object.

Changes the template for the __copy__ method to return cls.__new__(cls, **self.__dict__) instead of new_cls.__new__(cls, **self.__dict__)

Tagging Python committee:
@taxpon @frol @mbohlool @cbornet @kenjones-cisco @tomplus @Jyhess @arun-nalla @spacether

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  ./bin/utils/export_docs_generators.sh
  

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[spacether]

Closing and re opening to kick off ci

[spacether]

@tuanchien please fix the CI tests that are failing. I need them to be passing before I can approve and merge your PR.

[tuanchien]

@spacether I've rebased the latest master onto this branch and re-run bin/generate-samples.sh

Might need you to rerun the tests. The failures for node0,1,2 look related to the CI servers.

[tuanchien]

@spacether Rebased again off master today. All tests passing.

[spacether]

Looks great, thank you for the PR!