Fix bug fetching precondition params

lib/cwmp.js

@@ -357,7 +357,7 @@ function applyPresets(sessionContext) {
       path: v,
       pathGet: 1,
       pathSet: null,
-      attrGet: null,
+      attrGet: { value: 1 },
       attrSet: null,
       defer: true
     }));