test: make nodejsgh-2847 regression test stricter

Throw an error if either `err.message` or `err.code` is wrong.
Previously, it was only throwing an error if one or the other was
happening.

Author: Trott

test/parallel/test-child-process-fork-regr-gh-2847.js

@@ -56,8 +56,8 @@ var server = net.createServer(function(s) {
         // Ignore errors when sending the second handle because the worker
         // may already have exited.
         if (err) {
-          if ((err.message !== 'channel closed') &&
-             (err.code !== 'ECONNREFUSED')) {
+          if ((err.message !== 'channel closed') ||
+              (err.code !== 'ECONNREFUSED')) {
             throw err;
           }
         }