Introduces seen before routes in DefaultRoutingHandler

- to remember the routes that have been visited before

Change-Id: I96470ad5eb0837f7b734ba634c7c3d26e25d03ed
diff --git a/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java b/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
index 97436ab..745d2f8 100644
--- a/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
+++ b/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
@@ -1592,6 +1592,7 @@
 
         if (mastershipService.isLocalMaster(deviceId)) {
             defaultRoutingHandler.populatePortAddressingRules(deviceId);
+            defaultRoutingHandler.purgeSeenBeforeRoutes(deviceId);
             DefaultGroupHandler groupHandler = groupHandlerMap.get(deviceId);
             groupHandler.createGroupsFromVlanConfig();
             routingRulePopulator.populateSubnetBroadcastRule(deviceId);