[KUBERNETES] Respect the existing kubernetes container SPARK_LOCAL_DIRS env

Respect the user defined SPARK_LOCAL_DIRS container env when setup local dirs.

For example, we use hostPath for spark local dir.

But we do not mount the sub disks directly to the pod, we mount a root path for spark driver/executor pod.

For example, the root path is `/hadoop`.

And there are sub disks under that, likes `hadoop/1, /hadoop/2, /hadoop/3, /hadoop4`.

And we want to define the SPARK_LOCAL_DIRS in the driver/executor pod env.

But now, the user specified SPARK_LOCAL_DIRS does not work.