Patch problem of "invalid path"

os.path.join() acts weird when destination starts with a slash. For fix it, I suggest to remove it.

Author: Nicolas

bridges/python/tornado/filemanager.py

@@ -274,7 +274,7 @@ def extract(self, request):
 
     def upload(self, handler):
         try:
-            destination = handler.get_body_argument('destination', default='/')
+            destination = handler.get_body_argument('destination', default='/')[1:]
             for name in handler.request.files:
                 fileinfo = handler.request.files[name][0]
                 filename = fileinfo['filename']