Fix NPE caused by RoutingRulePopulator not initiated before linkHandler.init()

Change-Id: If21a2628c9d4e7687c26fda467240093dbc723c8
diff --git a/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java b/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
index 1f035d7..0e4373b 100644
--- a/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
+++ b/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
@@ -440,6 +440,7 @@
         routeService.addListener(routeListener);
         topologyService.addListener(topologyListener);
 
+        linkHandler.init();
         l2TunnelHandler.init();
 
         log.info("Started");