Improved port handling for integration tests
Improved port handling for integration tests

We can now run more than one test in parallel, because it lets the OS assign a free port to the container, and does not use a predefined port.

MicroserviceWorkshop/JenkinsWorkflowDockerSample,MicroserviceWorkshop/jwd_books,MicroserviceWorkshop/JenkinsWorkflowDockerSample,MicroserviceWorkshop/jwd_books