lib,test: update in preparation for linter update

ESLint 2.9.0 fixes some bugs that resulted in minor issues not being
caught by ESLint 2.7.0. Update instances of our code that will be
flagged when we upgrade to ESLint 2.9.0.

PR-URL: https://github.com/nodejs/node/pull/6498


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>