A cache rebuild is needed to anonymize webform submissions

Hi, thank you for sharing this nice little module.

I have an issue about webform submissions which are not IP anonymized unless the cache is rebuilt.

The cron runs fine, the database is correctly emptied on the remote_addr field in webform_submission table. But webform has a sort of cache which keeps the IP addresses viewable on the submissions list if the listed submissions were already rendered in this same list. If we run the cron before refreshing the submissions list, the newer items will be correctly IP anonymized.

If we export the data, the IP addresses which are still hanging in the cache are also kept in the exported csv.

Tested on Drupal 8.4.8.