config: pick any requested fields from post body in bulk list oper

Extra fields (beyond props+refs) are specified in POST body in
bulk list instead of query string.

Change-Id: I7184babc86cfec8b005aee05b3e487b08c5a3f62
Closes-Bug: #1473261

src/config/api-server/tests/test_crud_basic.py

@@ -1013,6 +1013,28 @@ def test_list_bulk_collection(self):
             parent_id=vn_uuids,
             filters={'display_name':'%s-ri-5' %(self.id())})
         self.assertThat(len(ret_list['routing-instances']), Equals(1))
+
+        logger.info("Querying VNs by obj_uuids for children+backref fields.")
+        flexmock(self._api_server).should_call('_list_collection').once()
+        ret_objs = self._vnc_lib.resource_list('virtual-network',
+            detail=True, obj_uuids=vn_uuids, fields=['routing_instances',
+            'virtual_machine_interface_back_refs'])
+
+        ret_ri_uuids = []
+        ret_vmi_uuids = []
+        for vn_obj in ret_objs:
+            ri_children = getattr(vn_obj, 'routing_instances',
+                'RI children absent')
+            self.assertNotEqual(ri_children, 'RI children absent')
+            ret_ri_uuids.extend([ri['uuid'] for ri in ri_children])
+            vmi_back_refs = getattr(vn_obj,
+                'virtual_machine_interface_back_refs',
+                'VMI backrefs absent')
+            self.assertNotEqual(ri_children, 'VMI backrefs absent')
+            ret_vmi_uuids.extend([vmi['uuid'] for vmi in vmi_back_refs])
+
+        self.assertThat(set(ri_uuids), Equals(set(ret_ri_uuids)))
+        self.assertThat(set(vmi_uuids), Equals(set(ret_vmi_uuids)))
     # end test_list_bulk_collection
 
     def test_list_lib_api(self):

src/config/api-server/vnc_cfg_api_server.py

@@ -1923,8 +1923,8 @@ def _list_collection(self, resource_type, parent_uuids=None,
             obj_class = self.get_resource_class(obj_type)
             obj_fields = list(obj_class.prop_fields) + \
                          list(obj_class.ref_fields)
-            if 'fields' in bottle.request.query:
-                obj_fields.extend(bottle.request.query.fields.split(','))
+            if req_fields:
+                obj_fields.extend(req_fields)
             (ok, result) = self._db_conn.dbe_read_multi(
                                 obj_type, obj_ids_list, obj_fields)