NO-JIRA: Clean up system_test.dir properly before running tests.

- Fix issues with creating incorrect sub-directories if setUpClass fails.

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/trunk@1605635 13f79535-47bb-0310-9956-ffa450edef68
NO-JIRA: Fix use of runpy.run_path for python < 2.7.

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/trunk@1605636 13f79535-47bb-0310-9956-ffa450edef68