add a list-item-level default for datasources/zones option

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/trac384@4127 e5f2f494-b856-4b98-b285-d166d9295462

src/bin/auth/auth.spec.pre.in

@@ -36,6 +36,7 @@
             { "item_name": "list_element",
               "item_type": "map",
               "item_optional": true,
+              "item_default": { "origin": "", "file": "" },
               "map_item_spec": [
               { "item_name": "origin",
                 "item_type": "string",