system_tests_grpc is failing on CentOS 9 proton main

[gabordozsa]

The grpc test started failing on various PRs.

Compile and Test (centos:stream9, RelWithDebInfo, OFF, proton main, shard 2 of 2) CI log tail:

/home/runner/work/skupper-router/skupper-router/skupper-router/tests/system_test.py:1514: in tearDownClass
    cls.tester.teardown()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <system_test.Tester object at 0x7f491492b550>

    def teardown(self):
        """Clean up (tear-down, stop or close) objects recorded via cleanup()"""
        self.cleanup_list.reverse()
        errors = []
        for obj in self.cleanup_list:
            try:
                for method in ["teardown", "tearDown", "stop", "close"]:
                    cleanup = getattr(obj, method, None)
                    if cleanup:
                        cleanup()
                        break
            except Exception as exc:
                errors.append(exc)
        if errors:
>           raise RuntimeError("Errors during teardown: \n\n%s" % "\n\n".join([str(e) for e in errors])) from errors[0]
E           RuntimeError: Errors during teardown: 
E           
E           Expecting value: line 1 column 1 (char 0)
E           
E           Expecting value: line 1 column 1 (char 0)

/home/runner/work/skupper-router/skupper-router/skupper-router/tests/system_test.py:1372: RuntimeError
---------------------- generated xml file: /__w/skupper-router/skupper-router/skupper-router/build/tests/junitxmls/system_tests_grpc.xml -----------------------
=================================================================== short test summary info ====================================================================
ERROR ::GrpcServiceMethodsTest::test_grpc_01_unary - ConnectionRefusedError: [Errno 111] Connection refused
ERROR ::GrpcServiceMethodsTest::test_grpc_02_bidirectional_stream - ConnectionRefusedError: [Errno 111] Connection refused
ERROR ::GrpcServiceMethodsTest::test_grpc_03_server_stream - ConnectionRefusedError: [Errno 111] Connection refused
ERROR ::GrpcServiceMethodsTest::test_grpc_04_client_stream - ConnectionRefusedError: [Errno 111] Connection refused
ERROR ::GrpcServiceMethodsTestOverTcpTls::test_grpc_04_client_stream - RuntimeError: Errors during teardown: 

Expecting value: line 1 column 1 (char 0)

Expecting value: line 1 column 1 (char 0)
=========================================================== 4 passed, 5 errors in 302.83s (0:05:02) ============================================================


97% tests passed, 1 tests failed out of 38

Total Test time (real) = 323.66 sec

The following tests FAILED:
	 56 - system_tests_grpc (Failed)