[Python AMQP] fix pylint on feature/eventhub/pyproto branch

[swathipil]

• fix pylint errors and:
• uncomment this section:

  azure-sdk-for-python/eng/pipelines/templates/steps/build-artifacts.yml

  Line 83 in dcacd0c

  # - template: /eng/pipelines/templates/steps/run_apistub.yml

• remove eventhub and checkpointstoreblob-aio:

  azure-sdk-for-python/eng/tox/allowed_pylint_failures.py

  Line 63 in dcacd0c

  "azure-eventhub",

[swathipil]

addressed