Pass digest method when signing timestamp node

Author: colm29

src/zeep/wsse/signature.py

@@ -244,7 +244,7 @@ def _signature_prepare(envelope, key, signature_method, digest_method):
     _sign_node(ctx, signature, envelope.find(QName(soap_env, "Body")), digest_method)
     timestamp = security.find(QName(ns.WSU, "Timestamp"))
     if timestamp != None:
-        _sign_node(ctx, signature, timestamp)
+        _sign_node(ctx, signature, timestamp, digest_method)
     ctx.sign(signature)
 
     # Place the X509 data inside a WSSE SecurityTokenReference within