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

Change-Id: I17d72338d4202117d08b3dca9463be35a87a0c1e
diff --git a/utils/misc/src/main/java/org/onlab/packet/pim/PIMHello.java b/utils/misc/src/main/java/org/onlab/packet/pim/PIMHello.java
index 9ad3fdb..4d42f32 100644
--- a/utils/misc/src/main/java/org/onlab/packet/pim/PIMHello.java
+++ b/utils/misc/src/main/java/org/onlab/packet/pim/PIMHello.java
@@ -23,6 +23,7 @@
 import java.util.HashMap;
 import java.util.Map;
 
+import static com.google.common.base.MoreObjects.toStringHelper;
 import static org.onlab.packet.PacketUtils.checkInput;
 
 public class PIMHello extends BasePacket {
@@ -115,4 +116,13 @@
             return hello;
         };
     }
+
+    @Override
+    public String toString() {
+        return toStringHelper(getClass())
+                .add("nbrIpAddress", nbrIpAddress.toString())
+                .add("priorityPresent", Boolean.toString(priorityPresent))
+                .toString();
+        // TODO: need to handle options
+    }
 }