First, we cannot do a global check for has_wordpress or needs_php,
as those are defined per nginx vhost. Second, I realized that this
was only working in the past because vhosts that had WordPress or
needed PHP were listed first in the nginx_vhosts dict.
This changes the logic to first check if any vhosts have WordPress
or need PHP, then sets a fact that we can use to decide whether to
run php-fpm tasks or not.
