test: load common.js to test for global leaks

common.js contains code that checks for variables leaking into the
global namespace. Load common.js in all tests that do not
intentionally leak variables.

PR-URL: https://github.com/nodejs/node/pull/3095


Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>