`clean-task-policy` support `All` when submitting tfjobs

[1202zhyl]

arena should support clean-task-policy "All" when training via tfjobs. currently, only supports "Running"(clean RUNNING pod) or None(do nothing). when job is done, often we need to remove ps, chief, evaluator and worker.

[cheyang]

@1202zhyl would you like to contribute?

[hzliangbin]

@cheyang I'm just using kubeflow recently and quite interested in this issue. may I take it ?

[hzliangbin]

/assign