[CORD-438] Fix Segment Routing application

Changes:
- Discards Link events if one of the switch is down;
- Triggers the paths optimization after device-down event;

Change-Id: I4114f2450401e0d1ff5658d592daf319d977f20e
diff --git a/src/main/java/org/onosproject/segmentrouting/DefaultRoutingHandler.java b/src/main/java/org/onosproject/segmentrouting/DefaultRoutingHandler.java
index 870ea06..d7e4c3c 100644
--- a/src/main/java/org/onosproject/segmentrouting/DefaultRoutingHandler.java
+++ b/src/main/java/org/onosproject/segmentrouting/DefaultRoutingHandler.java
@@ -662,6 +662,7 @@
         if (updatedEcmpSpgMap != null) {
             updatedEcmpSpgMap.remove(deviceId);
         }
+        this.populateRoutingRulesForLinkStatusChange(null);
     }
 
     private final class RetryFilters implements Runnable {