[k8s] Fix generate_kubeconfig.sh when ingress is not used #15835

Job	Run time
python-test (3.8, tests/unit_tests)	6m 40s
python-test (3.8, tests/test_api.py)	3m 55s
python-test (3.8, tests/test_cli.py)	4m 13s
python-test (3.8, tests/test_config.py)	4m 4s
python-test (3.8, tests/test_global_user_state.py)	4m 6s
python-test (3.8, tests/test_jobs.py)	4m 32s
python-test (3.8, tests/test_list_accelerators.py)	4m 11s
python-test (3.8, tests/test_optimizer_dryruns.py)	5m 39s
python-test (3.8, tests/test_optimizer_random_dag.py)	4m 21s
python-test (3.8, tests/test_storage.py)	4m 6s
python-test (3.8, tests/test_wheels.py)	4m 3s
python-test (3.8, tests/test_jobs_and_serve.py)	3m 55s
python-test (3.8, tests/test_yaml_parser.py)	3m 55s
	57m 40s

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