admin: Add rp0.internal.admin.swh.network reverse proxy for admin nodes
Related to T2935
Test Plan
vagrant up admin-rp0 vagrant up admin-bardo
edit local /etc/hosts to add 10.168.50.20 as hedgedoc.softwareheritage.org $ curl -k https://hedgedoc.softwareheritage.org => happy
Migrated from D4823 (view on Phabricator)