SlapOSTool: Timestamp must use Slave Instance Modification Date as failover for getBangTimestamp

  If we do otherwise, and if the timestamp is propagated (send in another request), there is a chain of infinity
  recursive bangs

master/product/Vifib/Tool/SlapTool.py

@@ -1542,7 +1542,7 @@ class SlapTool(BaseTool):
         slave_instance = _assertACI(slave_instance.getObject())
         # XXX Use catalog to filter more efficiently
         if slave_instance.getSlapState() == "start_requested":
-          newtimestamp = int(slave_instance.getBangTimestamp(int(software_instance.getModificationDate())))                  
+          newtimestamp = int(slave_instance.getBangTimestamp(int(slave_instance.getModificationDate())))
           append({
             'slave_title': slave_instance.getTitle().decode("UTF-8"),
             'slap_software_type': \