Currently, we only set the service account for JobManager. The TaskManager is using the default service account. Before the KubernetesHAService is introduced, it works because the TaskManager does not need to access the K8s resource(e.g. ConfigMap) directly. But now the TaskManager needs to watch ConfigMap and retrieve leader address. So if the default service account does not have enough permission, users could not specify a valid service account for TaskManager.
We should introduce a new config option for TaskManager service account.