CORD-1583 More bug fixes in dual-ToR scenarios

 - reentrant lock was not being used correctly
 - fixHashGroup in group handler was not updating global store correctly
 - linkUp was not being noted in seenLinks if configuration came after switches connected
 - serialization error in global objective store due to missing kryo for Sets
 - damaged routepath computation was not taking pair-devs into account
 - switch failures were leading to improper ecmpSpg graph updates, and missed hash-group changes
 - implemented more next-objective verification as group sub-system can go out-of-sync with objective-store

Change-Id: If3cfdd715e9b69820894b49def31f75ceb748863
diff --git a/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java b/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
index fcf6dc7..477b466 100644
--- a/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
+++ b/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
@@ -20,6 +20,8 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
+
 import org.onlab.packet.ChassisId;
 import org.onlab.packet.EthType;
 import org.onlab.packet.Ip4Address;
@@ -272,6 +274,7 @@
                       LinkedHashSet.class
             )
             .register(HashMultiset.class)
+            .register(Sets.class)
             .register(Maps.immutableEntry("a", "b").getClass())
             .register(new ArraysAsListSerializer(), Arrays.asList().getClass())
             .register(Collections.singletonList(1).getClass())