networkcache SHOULD NOT complain if no signature is given

slapos/libnetworkcache.py

@@ -283,10 +283,13 @@ class NetworkcacheClient(object):
       raise DirectoryNotFound('It was impossible to parse json response:\n%s'%
         traceback.format_exc())
     filtered_data_list = []
+    if self.signature_certificate_list is not None:
       for data in data_list:
         if len(data[1]):
           if self._verifySignatureInCertificateList(data[0], data[1]):
             filtered_data_list.append(data)
+    else:
+      filtered_data_list = data_list
 
     if len(filtered_data_list) == 0:
       raise DirectoryNotFound('Could not find a trustable entry.')