Field-images wont be migrated in a migrate-upgrade --- Not sure if it's a bug
You've included a critical piece of information here which was not included in https://www.drupal.org/node/2759309:

You specified your file path as /var/www/html/benia.biz/sites/default/files.

Actually it should be /var/www/html/benia.biz/. 

The sites/default/files portion is automatically included in the file paths by the migration process.


In the correct path note you have an extra slash (one after the benia.biz so it's benia.biz/); Missing this slash as well could make the migration process miss the images.