Add a server alias for routes.yaml

The puppetlabs-puppetdb module used to configure puppetdb and its terminus, creates a routes.yaml to configure various termini. The file defines a hash where each key is the name of a puppet application and the termini each indirected class should be using. See https://github.com/puppetlabs/puppetlabs-puppetdb/blob/78b9df2f20d623ad59259ad8b507cb322484473a/manifests/master/routes.pp#L7

Puppet should add an alias so that when routes.yaml is parsed, it accepts either server or master applications.

/cc austin.blatt