fix broken unit test

lib/http-server.js

@@ -173,7 +173,7 @@ function HttpServer(options) {
     serverOptions.https = options.https;
   }
 
-  this.server = options.https.passphrase
+  this.server = serverOptions.https && serverOptions.https.passphrase
     // if passphrase is set, shim must be used as union does not support
     ? require('./shims/https-server-shim')(serverOptions)
     : union.createServer(serverOptions);