Add docker dependency option to oras in setup.py

[Cyclam]

The Oras library we use has the Python docker module as an optional requirement. We do use that branch of Oras's code, so need the module. We didn't have the optional requirement turned on, so if you didn't already have the Python docker module installed, the AOSM CLI broke.

This PR adds the docker option into setup.py.

Testing

Tobias Weiserth hit this. Confirmed fixed after this change.

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