module: rename anonymous functions

This is my first contribution! #GoodnessSquad https://github.com/nodejs/node/issues/8913

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• [X ] commit message follows commit guidelines

Affected core subsystem(s)

#GoodnessSquad