Added a pipeline file (tests/azure/build-containers.yml) to build test
containers and upload them to quay.io. The pipeline will create
containers with IPA pre-installed for testing proposes on three
different Linux containers: CentOS 7, CentOS 8 and Fedora Latest.

* Adapted tests/test_playbook_runs.py script to allow tests to be
  executed from a docker container.
* Added molecule scenarios to create/destroy test containers and
  respective documentation in tests/README.md.