modified method return value

Signed-off-by: “wangxiyue” <wangxiyue8@huawei.com>

runtime/main/extend/systemplugin/napi/ohos_data_distributedDataObject.js

@@ -71,7 +71,7 @@ export function mockDistributedObject() {
     genSessionId: function (...args) {
       console.warn("distributedObject.genSessionId interface mocked in the Previewer." +
         " How this interface works on the Previewer may be different from that on a real device.");
-      return 'just test';
+      return paramMock.paramStringMock;
     }
   };
   return distributedDataObject;