Remove warnings from kubernetes tests (#22190)
Remove warnings from kubernetes tests (#22190)

There are warnings generated during K8S tests that there is a
group access to kubeconfig file.

This change makes the kubeconfig only accessible to user.
cfei18/incubator-airflow,lyft/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,apache/airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,apache/airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow,apache/airflow,apache/airflow,danielvdende/incubator-airflow,apache/airflow,apache/airflow,cfei18/incubator-airflow,lyft/incubator-airflow,lyft/incubator-airflow,danielvdende/incubator-airflow