Slow down some of the network updates.

lib/worker.js

@@ -8,6 +8,7 @@ const sock = zmq.socket('pub');
 let threadName = "Worker Server ";
 let cycleCount = 0;
 sock.bindSync('tcp://127.0.0.1:3000');
+let lastBlockHash = null;
 
 function updateShareStats() {
     // This is an omni-worker to deal with all things share-stats related
@@ -432,7 +433,8 @@ function updatePoolInformation() {
 
 function updateBlockHeader() {
     global.support.rpcDaemon('getlastblockheader', [], function (body) {
-        if (body.result) {
+        if (body.result && body.result.block_header.hash !== lastBlockHash) {
+            lastBlockHash = body.result.block_header.hash;
             global.database.setCache('networkBlockInfo', {
                 difficulty: body.result.block_header.difficulty,
                 hash: body.result.block_header.hash,