url: fix inconsistent port in url.resolveObject

This commit fixes bug where url.resolveObject returns conflicting
host and port values.

Fixes: https://github.com/nodejs/node/issues/8213
PR-URL: https://github.com/nodejs/node/pull/8214
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/url.js

@@ -776,6 +776,7 @@ Url.prototype.resolveObject = function(relative) {
     // it's absolute.
     if (relative.host || relative.host === '') {
       result.host = relative.host;
+      result.port = relative.port;
       result.auth = null;
     }
     if (relative.hostname || relative.hostname === '') {

test/parallel/test-url.js

@@ -1540,6 +1540,11 @@ var relativeTests2 = [
    'http://asdf:qwer@www.example.com',
    'http://diff:auth@www.example.com/'],
 
+  // changing port
+  ['https://example.com:81/',
+   'https://example.com:82/',
+   'https://example.com:81/'],
+
   // https://github.com/nodejs/node/issues/1435
   ['https://another.host.com/',
    'https://user:password@example.org/',