api/metadata/vendordata_dynamic: don't import Requests for its constants

Python-requests isn't really needed, don't import it to prevent
copy/paste of the anti pattern of accessing it's codes directly.

Fix one unit test that was returning a 204 but actually including data
in it, but expecting that data to not be used.

Change-Id: I9f6eda0c3e6f7d390abca5e9e4ebe059788ee11f

nova/api/metadata/vendordata_dynamic.py

@@ -15,7 +15,6 @@
 
 """Render vendordata as stored fetched from REST microservices."""
 
-import requests
 import six
 import sys
 
@@ -97,9 +96,7 @@ class DynamicVendorData(vendordata.VendorDataDriver):
             res = self.session.request(url, 'POST', data=jsonutils.dumps(body),
                                        verify=verify, headers=headers,
                                        timeout=timeout)
-            if res.status_code in (requests.codes.OK,
-                                   requests.codes.CREATED,
-                                   requests.codes.ACCEPTED):
+            if res:
                 # TODO(mikal): Use the Cache-Control response header to do some
                 # sensible form of caching here.
                 return jsonutils.loads(res.text)