Suggested fix

//FIND - NetworkUsageTask.run():

Transaction txn = Transaction.open(Transaction.CLOUD_DB);
                                    try {
                                        if ((answer.getBytesReceived() == 0) && (answer.getBytesSent() == 0)) {
                                            s_logger.debug("Recieved and Sent bytes are both 0. Not updating user_statistics");
                                            continue;
                                        }


//ADD AFTER:
                                        long routerNetworkID = 0;
                                        for (Nic routerNic2 : routerNics) {
                                            Network network2 = _networkMgr.getNetwork(routerNic2.getNetworkId());
                                            if (network2.getTrafficType() == TrafficType.Guest) {
                                                routerNetworkID = network2.getId();
                                            }
                                        }
//END ADDS;

//==========================================================================================

//FIND
UserStatisticsVO stats = _statsDao.lock(router.getAccountId(), router.getDataCenterIdToDeployIn(), network.getId(), routerNic.getIp4Address(), router.getId(), router.getType().toString());

//REPLACE IT WITH:
UserStatisticsVO stats = _statsDao.lock(router.getAccountId(), router.getDataCenterIdToDeployIn(), routerNetworkID, null, router.getId(), router.getType().toString());

//==========================================================================================

//FIND - NetworkStatsUpdateTask.prepareStop()
 if (answer != null) {
                        if (!answer.getResult()) {
                            s_logger.warn("Error while collecting network stats from router: "+router.getInstanceName()+" from host: "+router.getHostId() + "; details: " + answer.getDetails());
                            continue;
                        }
                        Transaction txn = Transaction.open(Transaction.CLOUD_DB);
                        try {
                            if ((answer.getBytesReceived() == 0) && (answer.getBytesSent() == 0)) {
                                s_logger.debug("Recieved and Sent bytes are both 0. Not updating user_statistics");
                                continue;
                            }

//ADD AFTER:
                            long routerNetworkID = 0;
                            for (Nic routerNic2 : routerNics) {
                                Network network2 = _networkMgr.getNetwork(routerNic2.getNetworkId());
                                if (network2.getTrafficType() == TrafficType.Guest) {
                                    routerNetworkID = network2.getId();
                                }
                            }
//END ADDS;

//==========================================================================================

//FIND
UserStatisticsVO stats = _statsDao.lock(router.getAccountId(), router.getDataCenterIdToDeployIn(), network.getId(), null, router.getId(), router.getType().toString());

//REPLACE IT WITH:
UserStatisticsVO stats = _statsDao.lock(router.getAccountId(), router.getDataCenterIdToDeployIn(), routerNetworkID, null, router.getId(), router.getType().toString());