Reflect DiffServ/TrafficClass when constructing ICMP/ICMP6 reply

Change-Id: I0c440a9270e5d560a23552514bcb89dc7dcbecb0
diff --git a/utils/misc/src/main/java/org/onlab/packet/ICMP.java b/utils/misc/src/main/java/org/onlab/packet/ICMP.java
index 9513061..bed5ab9 100644
--- a/utils/misc/src/main/java/org/onlab/packet/ICMP.java
+++ b/utils/misc/src/main/java/org/onlab/packet/ICMP.java
@@ -251,6 +251,7 @@
         ipReply.setDestinationAddress(ipRequest.getSourceAddress());
         ipReply.setSourceAddress(destAddress);
         ipReply.setTtl((byte) 64);
+        ipReply.setDiffServ(ipRequest.getDiffServ());
         ipReply.setChecksum((short) 0);
         ipReply.setProtocol(IPv4.PROTOCOL_ICMP);