All OpenStack heat requests must contain User/Key.

Updates the OpenStack Orchestration request() method
so that all requests contain the X-Auth-User and X-Auth-Key
headers.

Heat requires these parameters so that it can make subsequent requests
based on the users behalf.

For reference see here:

https://github.com/openstack/python-heatclient/blob/master/heatclient/common/http.py#L186