ifaces that correspond to endpoints on nodes. Makes it easier to
do something like this, if we init the interfaces on the nodes with IP
and mask and bring it up.

	# Add a raw PC to the request and give it an interface.
	node1 = request.RawPC("node1")
	iface1 = node1.addInterface()

	# Specify the IPv4 address
	iface1.addAddress(pg.IPv4Address("192.168.1.1", "255.255.255.0"))

	# Add another raw PC to the request and give it an interface.
	node2 = request.RawPC("node2")
	iface2 = node2.addInterface()

	# Specify the IPv4 address
	iface2.addAddress(pg.IPv4Address("192.168.1.2", "255.255.255.0"))

	# Add L1 link from node1 to node2
	link1 = request.L1Link("link1")
	link1.addInterface(iface1)
	link1.addInterface(iface2)