[ONOS-6783] Data type handling in Data Node

Change-Id: I5d27e169f95e2a5af89a866c1d34281201c73c56
diff --git a/serializers/xml/src/test/resources/food.yang b/serializers/xml/src/test/resources/food.yang
index 4c87fa0..861ef3a 100644
--- a/serializers/xml/src/test/resources/food.yang
+++ b/serializers/xml/src/test/resources/food.yang
@@ -44,7 +44,7 @@
            }
        }
        leaf p1 {
-           type string;
+           type empty;
        }
        leaf-list p2 {
            type string;