[AIRFLOW-5829] Get rid of the checklicence image.

[potiuk]

This change is a further step of simplifying the set of scripts
used by CI. The separate checklicence image was implemented as an
optimisation of the licence check time. The image to download was
small and could be downloaded slightly faster in CI. However that
made all the management script more complex and lead to having
separate jobs for check licence and static checks. That lead to
actually longer time of Travis jobs - because new machine had to
be spun-off for checklicence check only.

With this change, the CI image is the only one left and it is slightly
bigger (with RAT tool added) but the same image is used for all the
tests - unit tests, static checks and checklicence checks.

This also makes it easier to manage the images and decreases update
overhead on the developers using Breeze.

Make sure you have checked all steps below.

Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-5829

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Tests

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  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

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  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

[potiuk]

This one is green. Looking forward to merging this one as well (getting rid of checklicence image).

[potiuk]

And we have now one static check job in Travis run with single image - less overhead for starting VMs on Travis. See https://travis-ci.org/apache/airflow/builds/607930228

[potiuk]

Note that this build lasts longer but when we merge to master the image will be pushed to Dockerhub (I will speed it up with my build server in GCP) and they will be much faster (10 minutes each).