remove the r = Qdrouterd() pattern, use context

Make sure a router exits if an initial HTTP listener fails, doesn't hang ... FAIL
/usr/lib64/python3.10/unittest/case.py:613: ResourceWarning: unclosed file <_io.BufferedWriter name=6>
  outcome.errors.clear()
ResourceWarning: Enable tracemalloc to get the object allocation traceback

tests/system_tests_http.py

@@ -86,8 +86,8 @@ def test_listen_error(self):
             ('router', {'mode': 'standalone', 'id': 'bad'}),
             ('listener', {'port': listen_port, 'maxFrameSize': '2048', 'stripAnnotations': 'no'}),
             ('listener', {'port': listen_port, 'http': True})])
-        r = Qdrouterd(name="expect_fail", config=config, wait=False)
-        self.assertEqual(1, r.wait())
+        with Qdrouterd(name="expect_fail", config=config, wait=False) as r:
+            self.assertEqual(1, r.wait())
 
     def is_get_request_failing(self, url, use_ca=True, use_get_cert=False):
         try: