fix ARP (single onos instance & multiple onos instances)

1. make sure that ARP requests coming from host in a LAN
   are not broadcasted to all other edge ports (other ASes)
2. make sure the ARP requests from BGPd host can be singlecast
   to other ASes
3. add a 'get external network switch ports' function
4. make the arp work for both single onos instance & multiple
   onos instances
5. add a switch ports blacklist. Arp requests are not to be sent
   to those switch ports on this list.

Change-Id: I4ffdd73e2ad202517c54690a86109cfa1fbe400f
diff --git a/src/main/java/net/onrc/onos/core/packetservice/PacketOutNotification.java b/src/main/java/net/onrc/onos/core/packetservice/PacketOutNotification.java
index 2a577f3..11a1015 100644
--- a/src/main/java/net/onrc/onos/core/packetservice/PacketOutNotification.java
+++ b/src/main/java/net/onrc/onos/core/packetservice/PacketOutNotification.java
@@ -1,6 +1,5 @@
 package net.onrc.onos.core.packetservice;
 
-import java.io.Serializable;
 import java.util.Arrays;
 
 import net.onrc.onos.core.topology.MutableTopology;
@@ -13,9 +12,7 @@
  * abstract base class that will be subclassed by specific types of
  * notifications.
  */
-public abstract class PacketOutNotification implements Serializable {
-
-    private static final long serialVersionUID = 1L;
+public abstract class PacketOutNotification {
 
     private final byte[] packet;