metacafe extractor: deal with family filter

If you don't send this user=ffilter: false cookie, it will 301 redirect you to a page asking about it, and then the title check will fail.

youtube_dl/extractor/metacafe.py

@@ -148,8 +148,9 @@ class MetacafeIE(InfoExtractor):
         # AnyClip videos require the flashversion cookie so that we get the link
         # to the mp4 file
         headers = {}
+        headers['Cookie'] = 'user=%7B%22ffilter%22%3Afalse%7D;';
         if video_id.startswith('an-'):
-            headers['Cookie'] = 'flashVersion=0;'
+            headers['Cookie'] += ' flashVersion=0;'
 
         # Retrieve video webpage to extract further information
         webpage = self._download_webpage(url, video_id, headers=headers)