Set any one of Ethernet (MAC) address, IP address or IP netmask for
        a given interface on a node.

def setInterfaceAddresses(self, node, interface, mac=None, ip=None, netmask=None):
        '''
        Set any one of Ethernet (MAC) address, IP address or IP netmask for
        a given interface on a node.
        '''
        if not self.hasNode(node):
            raise Exception("No such node {}".format(node))
        nobj = self.getNode(node)['nodeobj']
        if interface not in nobj:
            raise Exception("No such interface {}".format(interface))

        intf = nobj.getInterface(interface)
        if mac:
            intf.ethaddr = mac
        if ip:
            intf.ipaddr = ip
        if netmask:
            intf.netmask = netmask