Stop proxyarp from handling mcast packets and a configuration item to
stop fwd from handling mcast packets.  FWD & ProxyArp checks the IPv4
mac address to determine if the packet is multicast.

Change-Id: Ibf1c207635badea2f3d2a824e8574f352bfbab16
diff --git a/apps/proxyarp/src/main/java/org/onosproject/proxyarp/ProxyArp.java b/apps/proxyarp/src/main/java/org/onosproject/proxyarp/ProxyArp.java
index 6586a4e..136a418 100644
--- a/apps/proxyarp/src/main/java/org/onosproject/proxyarp/ProxyArp.java
+++ b/apps/proxyarp/src/main/java/org/onosproject/proxyarp/ProxyArp.java
@@ -223,6 +223,14 @@
             if (!ipv6NeighborDiscovery && (ethPkt.getEtherType() == TYPE_IPV6)) {
                 return;
             }
+
+            // Do not ARP for multicast packets.  Let mfwd handle them.
+            if (ethPkt.getEtherType() == Ethernet.TYPE_IPV4) {
+                if (ethPkt.getDestinationMAC().isMulticast()) {
+                    return;
+                }
+            }
+
             //handle the arp packet.
             proxyArpService.handlePacket(context);
         }