Support ambari behind a reverse proxy, and also starting of services.

[steve-gh]

No description provided.

[jimbobhickville]

Unless I'm reading this wrong, it doesn't seem to handle path-based reverse proxies because it only matches to the first /. If the reverse proxy proxies all Ambari API requests under a /ambari path, such as https://proxy.host.com/ambari/api/v1/ -> https://ambari.host.com/api/v1 you'll end up with https://ambari.host.com/ambari/api/v1 instead, which won't be correct.

Also, this doesn't seem to account for QueryableModelCollection. Should we just put this in ambariclient.client.HttpClient.request so we can globally handle it?