Seeing the following traceback when autoscale attempts to get a token:

    Traceback (most recent call last):
      File "/opt/mimic/local/lib/python2.7/site-packages/twisted/web/http.py", line 790, in requestReceived
    2014-05-06_18:20:25.75897           self.process()
      File "/opt/mimic/local/lib/python2.7/site-packages/twisted/web/server.py", line 189, in process
    2014-05-06_18:20:25.75898           self.render(resrc)
      File "/opt/mimic/local/lib/python2.7/site-packages/twisted/web/server.py", line 238, in render
    2014-05-06_18:20:25.75898           body = resrc.render(self)
      File "/opt/mimic/local/lib/python2.7/site-packages/klein/resource.py", line 91, in render
        **kwargs)
    2014-05-06_18:20:25.75899       --- <exception caught here> ---
      File "/opt/mimic/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 137, in maybeDeferred
    2014-05-06_18:20:25.75899           result = f(*args, **kw)
      File "/opt/mimic/local/lib/python2.7/site-packages/klein/app.py", line 79, in execute_endpoint
        return endpoint_f(self._instance, *args, **kwargs)
      File "/opt/mimic/local/lib/python2.7/site-packages/klein/app.py", line 162, in _f
        return call(instance, f, request, *a, **kw)
      File "/opt/mimic/local/lib/python2.7/site-packages/klein/app.py", line 138, in call
    2014-05-06_18:20:25.75900           return f(instance, *args, **kwargs)
      File "/mnt/hgfs/mimic/mimic/rest/auth_api.py", line 35, in get_service_catalog_and_token
        auth_user_name = content['auth'][credential_key[0]]['username']
    exceptions.TypeError: string indices must be integers

In this case, autoscale is also passing the `tenantName`, and the JSON blob passed looks like:

    {
        "auth": {
            "tenantName": ...,
            "passwordCredentials": {
                "username": ...,
                "password": ...
             }
         }
     }

`credential_key[0]` is "tenantName", not "passwordCredentials".  Maybe the check should be for either "passwordCredentials" or "apiKeyCredentials" specifically?