Remove listeners before shutting down the executors

Change-Id: I1496ec06a839bb893e35a2e6d322d9eed33f45f2
diff --git a/apps/segmentrouting/app/src/main/java/org/onosproject/segmentrouting/xconnect/impl/XconnectManager.java b/apps/segmentrouting/app/src/main/java/org/onosproject/segmentrouting/xconnect/impl/XconnectManager.java
index 7a579b2..102d469 100644
--- a/apps/segmentrouting/app/src/main/java/org/onosproject/segmentrouting/xconnect/impl/XconnectManager.java
+++ b/apps/segmentrouting/app/src/main/java/org/onosproject/segmentrouting/xconnect/impl/XconnectManager.java
@@ -250,6 +250,7 @@
         xconnectStore.removeListener(xconnectListener);
         deviceService.removeListener(deviceListener);
         hostService.removeListener(hostListener);
+        portLoadBalancerService.removeListener(portLoadBalancerListener);
         codecService.unregisterCodec(XconnectDesc.class);
 
         deviceEventExecutor.shutdown();