prop map must be written as map

At one place, it was being written as list. Fixed that.
Closes-Bug: 1540856

Change-Id: I098cf1761b9b0ff669a42bf6d3486bd770065cf7

src/config/common/vnc_cassandra.py

@@ -609,7 +609,7 @@ def object_update(self, res_type, obj_uuid, new_obj_dict):
                 map_key_name = obj_class.prop_map_field_key_names[prop_name]
                 for map_elem in map_coll:
                     map_key = map_elem[map_key_name]
-                    self._add_to_prop_list(bch, obj_uuid,
+                    self._set_in_prop_map(bch, obj_uuid,
                         prop_name, map_elem, map_key)
             else:
                 self._create_prop(bch, obj_uuid, prop_name, new_props[prop_name])