kernel bug lead to incorrect cpu usage

[sleepyzhang]

in one case，metrics-server will respons incorrect cpu usage，detailed description is as follows：
A StatefulSet pod named pod-0 used to run on a node named node1, this pod is then scheduled to run on node2，node1 has a kernel bug that causes the resource usage information of the pod-0 is stored，so when metrics-server pulls datas，which can pull pod-0 datas on node1 and node2, and drop node2's data， then when hpa controller gets pod-0 cpu usage will get a very large value，eg：pod-0 ran in node1 3 days ago,which used cpu accumulate 518400，and then pod-0 now running in node2 and used cpu accumulate 30， in this case, the calculated cpu usage is very large，the calcute way is described as follows:

1. subValue: 518400 - 30
2. windows: time.Now().Add(-324time.Hour).Sub(time.Now())
3. cpuUsage: subValue / windows = (518400 - 30) / time.Now().Add(-324time.Hour).Sub(time.Now()).Seconds()
4. res = uint64Qunatity(uint64(cpuUsage), resource.DecimalSI, -9)
5. res is 18446744074
   so when calcute cpu usage，needing add a judge about data's collected timestamp

[linux-foundation-easycla]

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• ✅ login: sleepyzhang (82a7323)

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[serathius]

/lgtm
/approve

Can you backport to v0.6?

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: serathius, sleepyzhang

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[serathius]

/hold

Please sign the CLA and add a test.

[dashpole]

/triage accepted

[sleepyzhang]

/lgtm /approve

Can you backport to v0.6?

/lgtm /approve

Can you backport to v0.6?

@serathius Does that mean I should mention a pr based on v0.6?

[sleepyzhang]

/hold

Please sign the CLA and add a test.

@serathius How do i add a test?

[serathius]

/retest

[serathius]

/unhold

[serathius]

/ok-to-test

[serathius]

/lgtm

[serathius]

/retest