results from class_setup_teardown don't indicate whether they came from setup or teardown phase

[mrtyler]

Effects of this can be seen in TestRunnerServerExceptionInSetupPhaseBaseTestCase:

        # self.run_test configures us up to collect results submitted at
        # class_teardown completion time. class_setup_teardown methods report
        # the result of their teardown phase at "class_teardown completion"
        # time. So, when testing the setup phase of class_setup_teardown, we
        # will see an "extra" method.

It would be clearer if we could inspect a TestResult and determine not just its fixture (class_setup_teardown) but which phase the result is reporting.