util: Remove p, has been deprecated for years

Update deprecation test to use another method.

Ref: https://github.com/nodejs/node/pull/2529
PR-URL: https://github.com/nodejs/node/pull/3432


Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>