(PUP-3642) Remove environment name from URL path

This commit makes some changes to the indirector network layer
such that the environment name is no longer a part of the main
URL path structure.  This will allow us to have a more finite URL space
and run Puppet in the same webserver with other apps, without
worrying about URL collisions.  Instead, the environment becomes a query
parameter.
Based off how this is used (https://github.com/cprice404/puppet/blob/feature/master/PUP-3642-remove-env-from-url-path/lib/puppet/indirector/rest.rb#L84-L92), it seems like the environment query param should be part of the "body", rather than part of the uri.