Use zap instead of klog

[xrstf]

What this PR does / why we need it:
This PR replaces klog with Zap. Why?

• We (as in Kubermatic GmbH) use Zap pretty much everywhere.
• Zap support exists in controller-runtime as well.
• klog is terribly useless for structured/contextual logging.
• I personally just immensely dislike klog. :-D

There were a few log messages on level 3, which is somewhere between INFO and DEBUG. I made a gut choice for all of those, trying to make the logs useful but not too verbose.

klog still remains for the debug HTTP client (as it depends on numeric log levels, something we cannot do with Zap) and for the e2e tests (their logs are kind of boring and don't need Zap that much).

What type of PR is this?
/kind feature

Does this PR introduce a user-facing change? Then add your Release Note here:

Logging was replaced with Zap; the klog-related CLI flags like `-logtostderr`, `-v` etc. have been removed; use `-log-debug=true/false` and `-log-format=text/json` instead.

Documentation:

NONE

[ahmedwaleedmalik]

/approve

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 4a183fc0e06e9448bd1c76b0fcfc0095648e5f02

[mfranczy]

/approve
/lgtm

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahmedwaleedmalik, mfranczy, xrstf

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• OWNERS [ahmedwaleedmalik,mfranczy,xrstf]
• pkg/cloudprovider/provider/kubevirt/OWNERS [mfranczy]

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[kubermatic-triage-bot]

/retest
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[kubermatic-triage-bot]

/retest
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Review the full test history

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[kubermatic-triage-bot]

/retest
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[kubermatic-triage-bot]

/retest
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[kubermatic-bot]

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

Test name	Commit	Details	Required	Rerun command
pull-machine-controller-e2e-openstack	9b58708	link	false	/test pull-machine-controller-e2e-openstack

Full PR test history

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[ahmedwaleedmalik]

/hold
To avoid retries.

@xrstf I'm not sure what's wrong with the VCD tests. You can create a ticket to fix these tests and then probably override them here on this PR.

pull-machine-controller-e2e-openstack is optional so we can ignore that.

[xrstf]

/override pull-machine-controller-e2e-vmware-cloud-director
/unhold

[kubermatic-bot]

@xrstf: Overrode contexts on behalf of xrstf: pull-machine-controller-e2e-vmware-cloud-director

In response to this:

/override pull-machine-controller-e2e-vmware-cloud-director
/unhold

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.