Un-tag and Prune TR Images properly (#118)

Author: Tyler Titsworth

test-runner/test_runner.py

@@ -205,7 +205,8 @@ def get_test_list(args: dict, tests_yaml: List[dict]):
         remaining_containers = docker.container.list()
         for container in remaining_containers:
             docker.stop(container, time=None)
-        docker.image.remove(test_images, force=True)
+        docker.image.remove(test_images, force=True, prune=False)
+        docker.system.prune()
         logging.info("%d Images Removed", len(test_images))
     # Print Summary Table
     logging.info(