NO-JIRA: system_test.py: Clean up after error in setUpClass.

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/trunk@1647384 13f79535-47bb-0310-9956-ffa450edef68
NO-JIRA: Fix unreasonably small timeout causing test failures.

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/trunk@1647385 13f79535-47bb-0310-9956-ffa450edef68