Nginx: Change www-origin vhost www_root
Nginx: Change www-origin vhost www_root

Change the root public directory for the `www-origin` Nginx virtual host
to use the `www.gov.uk` hostname.

This is to accommodate changes that we're making to the GOV.UK Crawler
Worker to write content in directories named after the HTTP host from
which they were crawled.

alphagov/govuk_mirror-puppet,alphagov/govuk_mirror-puppet,alphagov/govuk_mirror-puppet