The default value of the parameter in_cluster of the
kube_client.get_kube_client function is
in_cluster=conf.getboolean('kubernetes', 'in_cluster'). Therefore, the
expected behavior is that when, in_cluster is not set, it takes the
value in the configuration file.

However, the default value of in_cluster in KubernetesPodOperator.py is
False and in_cluster is passed as a parameter when calling the
kube_client.get_kube_client function. Therefore, it changes the
expecting behavior by overwritting the default value. When in_cluster is
not set when initializing KubernetesPodOperator, the value of in_cluster
in kube_client.get_kube_client is False and not the value which is in
the configuration file.

Therefore, the default value of in_cluster in KubernetesPodOperator has
been changed to None and will not be passed to get_kube_client if it is
not overwritten so that it takes the configuration value as a default
value.