credential: create assignmnent starting the day before today.

Funny things can happen if you have multiple machines and their clock are not
synchronized.

bt5/erp5_credential/SkinTemplateItem/portal_skins/erp5_credential/CredentialRequest_updatePersonAssignment.xml

@@ -107,7 +107,7 @@ for role in context.getRoleList():\n
         function = context.getFunctionList(),\n
         group = context.getGroupList(),\n
         destination = organisation_url,\n
-        start_date = today,\n
+        start_date = today - 1,\n
         stop_date = delay)\n
 \n
     assignment.open()\n

bt5/erp5_credential/bt/revision

-429
+430
\ No newline at end of file