test,lib,benchmark: match function names

In most cases, named functions match the variable or property to which
they are being assigned. That also seems to be the practice in a series
of PRs currently being evaluated that name currently-anonymous
functions.

This change applies that rule to instances in the code base that don't
comply with that practice.

This will be enforceable with a lint rule once we upgrade to ESLint
3.8.0.

PR-URL: https://github.com/nodejs/node/pull/9113


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>