terminationObserver: use lister instead of direct client calls

[vrutkovs]

Termination observer does not need to do direct client calls, instead it can rely on pod lister information.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: vrutkovs

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[openshift-ci]

@vrutkovs: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/e2e-aws-ovn	f185e28	link	true	/test e2e-aws-ovn
ci/prow/e2e-aws-operator-disruptive-single-node	f185e28	link	false	/test e2e-aws-operator-disruptive-single-node
ci/prow/e2e-aws-ovn-upgrade	f185e28	link	true	/test e2e-aws-ovn-upgrade
ci/prow/e2e-gcp-operator-single-node	f185e28	link	false	/test e2e-gcp-operator-single-node

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