Revert "Revert "Uses ICMPEcho class in OpenstackRoutingIcmpHandler and test class.""

This reverts commit 02db25c894157857844786a327d00c54bd470fb0.

Change-Id: Ie32f35f7f4cadad36842a58d38c958e6d55d88fc
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingIcmpHandler.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingIcmpHandler.java
index 67cedcc..b8eb339 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingIcmpHandler.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingIcmpHandler.java
@@ -23,6 +23,7 @@
 import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.onlab.packet.Ethernet;
 import org.onlab.packet.ICMP;
+import org.onlab.packet.ICMPEcho;
 import org.onlab.packet.IPv4;
 import org.onlab.packet.IpAddress;
 import org.onlab.packet.MacAddress;
@@ -421,7 +422,7 @@
     }
 
     private short getIcmpId(ICMP icmp) {
-        return ByteBuffer.wrap(icmp.serialize(), 4, 2).getShort();
+        return ((ICMPEcho) icmp.getPayload()).getIdentifier();
     }
 
     private class InternalPacketProcessor implements PacketProcessor {