tests: running cluster flacky test

tt_cmd = PosixPath('/private/tmp/pytest-of-tntmac04.tarantool.i/pytest-19/tt_build0/tt')
tmpdir_with_cfg = '/private/tmp/pytest-of-tntmac04.tarantool.i/pytest-19/test_running_env_variables0'

    def test_running_env_variables(tt_cmd, tmpdir_with_cfg):
        tmpdir = tmpdir_with_cfg
        # Copy the test application to the "run" directory.
        test_app_path = os.path.join(os.path.dirname(__file__), "test_env_app", "test_env_app.lua")
        shutil.copy(test_app_path, tmpdir)
    
        # Set environmental variable which changes log format to json.
        my_env = os.environ.copy()
        my_env["TT_LOG_FORMAT"] = "json"
    
        try:
            # Start an instance with custom env.
            start_cmd = [tt_cmd, "start", "test_env_app"]
            instance_process = subprocess.Popen(
                start_cmd,
                cwd=tmpdir,
                stderr=subprocess.STDOUT,
                stdout=subprocess.PIPE,
                text=True,
                env=my_env
            )
            start_output = instance_process.stdout.readline()
            assert re.search(r"Starting an instance", start_output)
    
            # Check status.
            file = wait_file(os.path.join(tmpdir, "test_env_app", run_path, "test_env_app"),
                             pid_file, [])
            assert file != ""
            status_cmd = [tt_cmd, "status", "test_env_app"]
            status_rc, status_out = run_command_and_get_output(status_cmd, cwd=tmpdir)
            assert status_rc == 0
            status_out = extract_status(status_out)
            assert status_out["test_env_app"]["STATUS"] == "RUNNING"
    
            # Check that log format is in json.
            logPath = os.path.join(tmpdir, "test_env_app", "var", "log", "test_env_app", log_file)
            wait_string_in_file(logPath, "{")
        finally:
            # Stop the Instance.
            stop_cmd = [tt_cmd, "stop", "-y", "test_env_app"]
            stop_rc, stop_out = run_command_and_get_output(stop_cmd, cwd=tmpdir)
            assert stop_rc == 0
>           assert re.search(r"The Instance test_env_app \(PID = \d+\) has been terminated.", stop_out)
E           AssertionError: assert None
E            +  where None = <function search at 0x104a6d5a0>('The Instance test_env_app \\(PID = \\d+\\) has been terminated.', '')
E            +    where <function search at 0x104a6d5a0> = re.search

test/integration/running/test_running.py:618: AssertionError
----------------------------- Captured stdout call -----------------------------
 INSTANCE      STATUS   PID    MODE  CONFIG  BOX  UPSTREAM 
 test_env_app  RUNNING  77940        --      --   --       

The status of some instances requires attention.
Please rerun the command with the --details flag to see more information


------------------------------ Captured log call -------------------------------
WARNING  retry.api:api.py:40 , retrying in 0.5 seconds...
=========================== short test summary info ============================
FAILED test/integration/running/test_running.py::test_running_env_variables - AssertionError: assert None
 +  where None = <function search at 0x104a6d5a0>('The Instance test_env_app \\(PID = \\d+\\) has been terminated.', '')
 +    where <function search at 0x104a6d5a0> = re.search