Fix: resolve IAE due to unregistered LinkedHashMap in Kryo registry

Change-Id: I74be59dd50c5bd3c942a6e9a42475825739b9693
diff --git a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/DistributedOpenstackNetworkStore.java b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/DistributedOpenstackNetworkStore.java
index 8e03ba5..4442c9a 100644
--- a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/DistributedOpenstackNetworkStore.java
+++ b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/DistributedOpenstackNetworkStore.java
@@ -55,6 +55,7 @@
 import org.openstack4j.openstack.networking.domain.NeutronSubnet;
 import org.slf4j.Logger;
 
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.ExecutorService;
@@ -99,6 +100,7 @@
             .register(IPVersionType.class)
             .register(Ipv6AddressMode.class)
             .register(Ipv6RaMode.class)
+            .register(LinkedHashMap.class)
             .build();
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)