lib,test: lint fixes for linter upgrade

ESLint 4.19.1 fixes some bugs in rules. These changes prepare us for the
upgrade.

PR-URL: https://github.com/nodejs/node/pull/19528


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>