www/mod_pagespeed: Fix distinfo by using LOCAL in MASTER_SITES
Some of Google's MASTER_SITES add some nonce to disfiles everytime we fetch,
Therefore the distinfo becomes incorrect.
We use our own LOCAL for those and update them with every update on port.

Reviewed by: mat (mentor)
Approved by: mat (mentor)
Sponsored by: Netzkommune GmbH
Differential Revision: https://reviews.freebsd.org/D12695