(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.
I think it just depends whether we want to be treating the environment as part of the uri or not. In the case of a request to `/node/foo?environment=production&otherarg1=blah&otherarg2=blah` this would get parsed such that

```
uri = /node/foo?environment=production
body = otherarg1=blah&otherarg2=blah
```
would be send in the POST. It seems a little weird to have all the other query parameters be sent in the body in the POST, but not the environment. But it shouldn't actually matter at all, given the changes we are making for how params are parsed.