Fix warnings (SA9003, SA4023, SA1019)

[Honny1]

This PR fixes warnings (SA9003, SA4023, SA1019) found by golangci when the staticcheck linter is enabled.

Partially fixes:

• Consider allowing more linters #1579

[mtrmac]

Thanks! Code LGTM.

I especially appreciate having one commit per idea clearly separated.

Please squash the “Fix ignore of Using a deprecated function, variable, constant or field (SA1019)” and “Improve explanation of ignore deprecated code” commits; we don’t need both in the permanent history — and besides, it will serve as a practical example of git rebase -i.

[Honny1]

@mtrmac I have quashed commits.

[mtrmac]

/lgtm
/approve

Thanks!

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Honny1, mtrmac

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [mtrmac]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment