Take down edge ports on a leaf switch when all uplinks are gone

- Bug fix for case when all uplinks are gone, but dual-homed host continues to send packets to switch;
  We now administratively take down the host port to force the host to use the other leaf in the pair.
- Restructured SR manager by creating a LinkHandler
- fixed/added some log messages

Change-Id: I3722cd364dc8798b16891519bec165627e92bd87
diff --git a/apps/segmentrouting/src/test/java/org/onosproject/segmentrouting/HostHandlerTest.java b/apps/segmentrouting/src/test/java/org/onosproject/segmentrouting/HostHandlerTest.java
index cce5a31..e33a36d 100644
--- a/apps/segmentrouting/src/test/java/org/onosproject/segmentrouting/HostHandlerTest.java
+++ b/apps/segmentrouting/src/test/java/org/onosproject/segmentrouting/HostHandlerTest.java
@@ -212,6 +212,7 @@
         srManager.cfgService = mockNetworkConfigRegistry;
         mockLocationProbingService = new MockLocationProbingService();
         srManager.probingService = mockLocationProbingService;
+        srManager.linkHandler = new MockLinkHandler(srManager);
 
         hostHandler = new HostHandler(srManager);