Carry previous alternative routes in ALTERNATIVE_ROUTES_CHANGED event

Change-Id: I393f4cb258a7b7824b4a6811e430c04acb6bd441
diff --git a/apps/route-service/app/src/main/java/org/onosproject/routeservice/impl/DefaultResolvedRouteStore.java b/apps/route-service/app/src/main/java/org/onosproject/routeservice/impl/DefaultResolvedRouteStore.java
index 34aeaa7..4981932 100644
--- a/apps/route-service/app/src/main/java/org/onosproject/routeservice/impl/DefaultResolvedRouteStore.java
+++ b/apps/route-service/app/src/main/java/org/onosproject/routeservice/impl/DefaultResolvedRouteStore.java
@@ -149,7 +149,7 @@
 
                 if (!immutableAlternatives.equals(oldRoutes)) {
                     return new RouteEvent(RouteEvent.Type.ALTERNATIVE_ROUTES_CHANGED,
-                            route, immutableAlternatives);
+                            route, null, immutableAlternatives, oldRoutes);
                 }
 
                 return null;