clean up cluster if tests are manually terminated

[edaniszewski]

right now, the cleanup of a test case will only happen after a test completes (whether passing or failed). if we manually bail out (e.g. ctrl+C), then the test does not get cleaned up and any test artifacts (namespace, cluster role bindings, etc) are left hanging around. we'll need to force the cleanup of any role with the kubetest: prefix and any namespace with the kubetest: prefix if we detect a manual termination.