changes to run tests from docker image

[PeterRJones]

This PR introduces some tweaks allowing the run_tests script to be run from within the Docker container. This is advantageous for it more closely mirrors the run-time environment. Reviewed and updated after consultation with @joseph-schaeffer

Changes:

• Updated Dockerfile to preserve pip and add pytest
• Created docker-compose-test to define test target and run time context to run tests (volume's and environment)
• Update run_tests script to display command and test output but mute JUnit output file. Fixed file flags on script file enabling execution. The JUnit output can be consumed by testing report or build such as Jenkins.

[CLAassistant]

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[PeterRJones]

Updated after review with @joseph-schaeffer