[WIP] Added golangci-lint for linting and fixed detected linting issues

[arjunrn]

Added golangci-lint as a make target which can be run as a check.
Also fixed issues which were reported by golangci-lint.

Discovered an issue with cvo_scenarios_test.go where the ClusterVersion resource was never actually updated in the fake client but always recreated. Fixed this which led to some knock on changes in the tests.

[openshift-ci]

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[openshift-ci]

@arjunrn: The following test failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
ci/prow/e2e-agnostic-upgrade	65596d8	link	/test e2e-agnostic-upgrade

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[LalatenduMohanty]

The code changes which fixes specific linting issues should be in a separate commit. For example all deadcode fixes should a single commit. All gofmt fixes should in one commit. This will help the review easier . Also will help if someone wants to track the history behind some change.

[arjunrn]

Closing in favor of #598