When the ansible k8s module is refreshing the tokens from the local kube
config, it should save those token to the kube config file.
If this is not done, this might break the next kube client call as the
token in the local kube config file is not valid anymore and refreshing
can fail.
This commit is adding an env var K8S_AUTH_PERSIST_CONFIG that can be
used to set this flag to true (default is false, same as current
behavior).
