[test] always define nbCores in pow integration tests

test/integration/branches_revert2.js

@@ -23,6 +23,7 @@ const MEMORY_MODE = true;
 const commonConf = {
   ipv4: '127.0.0.1',
   currency: 'bb',
+  nbCores:1,
   httpLogs: true,
   forksize: 3,
   sigQty: 1

test/integration/register-fork-blocks.js

@@ -20,6 +20,7 @@ describe("Fork blocks", function() {
     s1 = toolbox.server({
 
       // The common conf
+      nbCores:1,
       medianTimeBlocks: 1,
       avgGenTime: 11,
       udTime0: now,
@@ -35,6 +36,7 @@ describe("Fork blocks", function() {
     s2 = toolbox.server({
 
       // Particular conf
+      nbCores:1,
       switchOnHeadAdvance: 5,
       forksize,
 
@@ -47,6 +49,7 @@ describe("Fork blocks", function() {
     s3 = toolbox.server({
 
       // Particular conf
+      nbCores:1,
       switchOnHeadAdvance: 5,
       forksize,