Multicast on given interface

[msimonin]

Maybe the possibility of sending multicast packet on a given interface has to be implemented.
For example when I deploy a cluster using vagrant the multicast packets are sent on eth0 instead of eth1. Everything is fine when I force in the code to send packet over eth1.
In this case the following change are required :
HeartBeatMulticastReceiver and HeartBeatMulticastSender need mcastSocket_.setNetworkInterface(NetworkInterface.getByName(name of the interface)).

Matt