Use each process in order instead of using a random one

lib/hk-util.js

@@ -931,6 +931,7 @@ const workers = [];
 for (let i = 0; i < numCPUs; i++) {
     workers.push(fork('lib/check-signature.js'));
 }
+var nextWorker = 0;
 var initWorker = function (worker) {
     worker.on('message', function (res) {
         onChecked.fire(res);
@@ -1018,12 +1019,12 @@ HK.onChannelMessage = function (Env, Server, channel, msgStruct) {
 
         console.log(+new Date(), "Send verification request");
         // Send the request
-        const random = Math.floor(Math.random() * 4);
-        workers[random].send({
+        workers[nextWorker].send({
             txid: txid,
             msg: signedMsg,
             key: metadata.validateKey
         });
+        if (++nextWorker > numCPUs) { nextWorker = 0; }
     }).nThen(function () {
         // do checkpoint stuff...