In context of IPv6 the appropriate methods for setting & obtaining the
interfaces for multicasts are setNetworkInterface & getNetworkInterfaces.
However the legacy setInterface & getInterface methods need to be
supported but the InetAddress returned by getInterface can't be
guaranteed to be the same InetAddress that was set with setInterface.
This occurs when there is more than one address on the same
network interface (eg: IPv6 & IPv4 address). This should be fixed.