test: Changed assert.equal to assert.strictEqual

Updated test-cluster-send-deadlock.js to change
assert.equal to assert.strictEqual

PR-URL: https://github.com/nodejs/node/pull/9902
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-cluster-send-deadlock.js

@@ -10,7 +10,7 @@ var net = require('net');
 if (cluster.isMaster) {
   var worker = cluster.fork();
   worker.on('exit', function(code, signal) {
-    assert.equal(code, 0, 'Worker exited with an error code');
+    assert.strictEqual(code, 0, 'Worker exited with an error code');
     assert(!signal, 'Worker exited by a signal');
     server.close();
   });