[ONOS-3222] Implement toString method for each Packet class

Change-Id: I17d72338d4202117d08b3dca9463be35a87a0c1e
diff --git a/utils/misc/src/main/java/org/onlab/packet/ipv6/EncapSecurityPayload.java b/utils/misc/src/main/java/org/onlab/packet/ipv6/EncapSecurityPayload.java
index e46a126..13c0545 100644
--- a/utils/misc/src/main/java/org/onlab/packet/ipv6/EncapSecurityPayload.java
+++ b/utils/misc/src/main/java/org/onlab/packet/ipv6/EncapSecurityPayload.java
@@ -24,6 +24,7 @@
 
 import java.nio.ByteBuffer;
 
+import static com.google.common.base.MoreObjects.toStringHelper;
 import static org.onlab.packet.PacketUtils.checkInput;
 
 /**
@@ -185,4 +186,12 @@
             return encapSecurityPayload;
         };
     }
+
+    @Override
+    public String toString() {
+        return toStringHelper(getClass())
+                .add("securityParamIndex", Integer.toString(securityParamIndex))
+                .add("sequence", Integer.toString(sequence))
+                .toString();
+    }
 }