php exts jobs now fetch Zuul ref via git protocol

Jobs updated:
php-FastStringSearch-build
php-NativePreprocessor-build
php-luasandbox-build
php-wikidiff-build
php-wikidiff2-build
php-wmerrors-build

Change-Id: I4fbbc3e8fd71e14b582b81092530ca8977e5b2b3