test: refactor test-cluster-worker-events

Use assert.strictEqual() instead of assert.equal()

PR-URL: https://github.com/nodejs/node/pull/9994
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-cluster-worker-events.js

@@ -10,7 +10,7 @@ if (cluster.isMaster) {
   var worker = cluster.fork();
 
   worker.on('exit', function(code) {
-    assert.equal(code, OK);
+    assert.strictEqual(code, OK);
     process.exit(0);
   });
 
@@ -49,7 +49,7 @@ function check(m) {
   assert.deepEqual(messages[0], messages[1]);
 
   cluster.worker.once('error', function(e) {
-    assert.equal(e, 'HI');
+    assert.strictEqual(e, 'HI');
     process.exit(OK);
   });