[youtube] Only set language when necessary

We only need to set the language when we are using a login; otherwise it will always be English.

youtube_dl/extractor/youtube.py

@@ -191,6 +191,7 @@ def _confirm_age(self):
     def _real_initialize(self):
         if self._downloader is None:
             return
+        if self._get_login_info()[0] is not None:
             if not self._set_language():
                 return
         if not self._login():