outputs <none> for colums not found

[jianhuiz]

What this PR does / why we need it:

outputs <none> for columns specified by -o custom-columns but not found in object

currently kubectl outputs an error of "xxx is not found" when a column is not in the returned json (omitted because of empty value or no such field in the object type at all). This PR suppress this error but outputs <none> at that field. This makes it convenient to output the objects details, especially when getting objects of different type in one command.

example:

$ kubectl get deploy,rs,po -o custom-columns=NAMESPACE:.metadata.namespace,NAME:.metadata.name,REPLICAS:.status.replicas
NAMESPACE   NAME                      REPLICAS
default     deck                      1
default     deck-433074128            1
default     deck-433074128-vxcg9      <none>

Special notes for your reviewer:

Release note:

outputs `<none>` for columns specified by `-o custom-columns` but not found in object

@kubernetes/kubectl-reviewers

[dims]

/approve no-issue

[jianhuiz]

/assign @janetkuo

@kubernetes/sig-cli-maintainers
@kubernetes/sig-cli-pr-reviews

[dims]

/unassign @dims

[janetkuo]

/retest

[janetkuo]

/lgtm

[janetkuo]

/approve no-issue

[k8s-github-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dims, janetkuo, jianhuiz

Associated issue requirement bypassed by: janetkuo

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[k8s-github-robot]

/test all [submit-queue is verifying that this PR is safe to merge]

[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 51750, 53195, 53384, 53410). If you want to cherry-pick this change to another branch, please follow the instructions here.

[k8s-ci-robot]

@jianhuiz: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
pull-kubernetes-e2e-kops-aws	091a9df	link	/test pull-kubernetes-e2e-kops-aws

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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