Revert "Removes `cancel-us-users` drush task."

This reverts commit 6954a140fb40332a0ffd6bb15725f16b36dd325d.
Alter the user delete script to leave users untouched if they've created content.
Merge pull request #3548 from sergii-tkachenko/cancel-us-users-script-new

Restores and fixes `cancel-us-users` drush task