Cherry-pick #18817 to 7.x: Upgrade k8s.io/client-go and k8s keystore tests

[ChrsMark]

Cherry-pick of PR #18817 to 7.x branch. Original message:

What does this PR do?

This PR is a follow up for #18096.
Aims to add tests for k8s keystore internal functionality using a fake client for retrieving k8s secrets. An upgrade of k8s.io/client-go is needed in order to make use of the fake client (https://github.com/kubernetes/client-go/releases/tag/v0.18.3, https://pkg.go.dev/k8s.io/client-go@v0.18.3/kubernetes?tab=doc).

Upgrade procedure:

go get k8s.io/client-go@v0.18.3
mage vendor
make notice

Changes:

1. Upgrade k8s.io/client-go
2. Add tests for k8s keystore
3. Improve k8s testing by adding a wait phase until kube-state-metrics in order to avoid flakiness

Why is it important?

In order to cover k8s keystore Retrieve functionality.

[elasticmachine]

Pinging @elastic/integrations-platforms (Team:Platforms)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #18879 opened]

• Start Time: 2020-06-01T13:45:36.298+0000

• Duration: 78 min 59 sec

Test stats 🧪

Test	Results
Failed	0
Passed	6664
Skipped	1069
Total	7733

Steps errors

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• Name: Report to Codecov

  • Description: curl -sSLo codecov https://codecov.io/bash for i in auditbeat filebeat heartbeat libbeat metricbeat packetbeat winlogbeat journalbeat do FILE="${i}/build/coverage/full.cov" if [ -f "${FILE}" ]; then bash codecov -f "${FILE}" fi done

  • Duration: 2 min 22 sec

  • Start Time: 2020-06-01T14:18:32.134+0000

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