Stop pushing dummy values to shadir

See erp5@c45c2295

slapcache/signature.py

@@ -175,9 +175,6 @@ class Signature:
       # as it can be badly configured.
       'timestamp': time.time(),
       'token': ''.join([choice(ascii_lowercase) for _ in range(128)]),
-      # backward compatibility
-      'file': 'notused',
-      'urlmd5': 'notused'
     }
     try:
       sha512sum = self.shacache.upload(open(path, 'rb'), self.key, **metadata_dict)