Add unit test case for controller/disruption

[houjun41544]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Release note:

NONE

[houjun41544]

/assign @mikedanese

[idealhack]

/ok-to-test

[houjun41544]

/retest

[neolit123]

needs milestone to be included before code freeze.

[fejta-bot]

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/lifecycle stale

[idealhack]

@kubernetes/sig-apps-pr-reviews
/remove-lifecycle stale

[mikedanese]

This looks fine. It could be easily rolled into other tests in this package with a table test.

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: houjun41544, mikedanese

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• pkg/controller/OWNERS [mikedanese]

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[idealhack]

/test pull-kubernetes-godeps

[idealhack]

/test pull-kubernetes-integration