Fix data passed to policy engine on update

fix bug 1044218

The original resource status fetched to the db was not being
properly updated with the request body before feeding it to the
policy engine

Change-Id: I9f71e40edf44136a40fad1ef272696d6b3ea352d

quantum/api/v2/base.py

@@ -376,8 +376,7 @@ class Controller(object):
                           value['required_by_policy'] or
                           not 'default' in value)]
         orig_obj = self._item(request, id, field_list=field_list)
-        orig_obj.update(body)
-
+        orig_obj.update(body[self._resource])
         try:
             policy.enforce(request.context,
                            action,