Jsonify all OS orchestration requests.

Updates the Orchestration request method so that *all* request
bodies with JSON responses get converted to JSON.

The previous code failed to convert some HTTP 2xx responses to
JSON.
Fix orchestration request status codes.

Make the OpenStack Orchestration return codes match what
actually gets returned from Heat.
Merge pull request #2212 from dprince/orchestration_fixes

OpenStack Orchestration fixes