Support manifest on Kubernetes 1.16+

[Jeffwan]

Update Deployment apiVersion from extensions/v1beta1 to apps/v1

[Jeffwan]

/cc @jinchihe @andreyvelich

[k8s-ci-robot]

@Jeffwan: The following test failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
kubeflow-pytorch-operator-presubmit	af18022	link	/test kubeflow-pytorch-operator-presubmit

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[Jeffwan]

/cc @johnugeorge @gaocegege

Let's merge some pending PRs.

[andreyvelich]

/lgtm

[k8s-ci-robot]

New changes are detected. LGTM label has been removed.

[k8s-ci-robot]

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[Jeffwan]

PR #305 already includes this PR. I will close the issue