[1.7.x] cater for running tests from another directory than tests - applying existing pattern to newly added test_testcase_ordering as well

Backport of d11e836203 from master

tests/test_runner/test_discover_runner.py

@@ -104,6 +104,7 @@ class DiscoverRunnerTest(TestCase):
         self.assertEqual(count, 0)
 
     def test_testcase_ordering(self):
+        with change_cwd(".."):
             suite = DiscoverRunner().build_suite(["test_discovery_sample/"])
             self.assertEqual(
                 suite._tests[0].__class__.__name__,