minor Kryo related cleanup

Change-Id: I772fc1f776563d30f1a4081c6fddd5739d985263
diff --git a/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/PortNumberSerializer.java b/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/PortNumberSerializer.java
index 02805bb..3792966 100644
--- a/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/PortNumberSerializer.java
+++ b/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/PortNumberSerializer.java
@@ -14,7 +14,7 @@
         Serializer<PortNumber> {
 
     /**
-     * Default constructor.
+     * Creates {@link PortNumber} serializer instance.
      */
     public PortNumberSerializer() {
         // non-null, immutable