Scapy upgrade to 2.4.0.rc5

- many of the patches fd.io applies in test/patches/2.3.3 are now upstreamed in 2.4
- 2.4 adds support for IGMPv3 which is my main motivation for the upgrade

Change-Id: If2c0a524e3cba320b4a5d8cd07817c6ea2bf0c5a
Signed-off-by: Neale Ranns <nranns@cisco.com>

test/util.py

@@ -4,7 +4,7 @@ import socket
 import sys
 from abc import abstractmethod, ABCMeta
 from cStringIO import StringIO
-from scapy.layers.inet6 import in6_mactoifaceid
+from scapy.utils6 import in6_mactoifaceid
 
 from scapy.layers.l2 import Ether
 from scapy.packet import Raw