chore: Update pod metrics when pod is completed

[jigisha620]

Fixes #N/A

Description
At present Pod metrics controller continues to emit the unstarted_time_metrics when the pod is completed. This PR adds a fix that will stop emitting the unstarted_time_metrics when the pod is completed.

How was this change tested?
Added tests.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[coveralls]

Pull Request Test Coverage Report for Build 15329064463

Details

• 14 of 20 (70.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 81.874%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/controllers/metrics/pod/controller.go	14	20	70.0%

Totals
Change from base Build 15328058434:	0.0%
Covered Lines:	10231
Relevant Lines:	12496

---

💛 - Coveralls

[jonathan-innis]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jigisha620, jonathan-innis

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