Duplication of pages after the execution of nested pages migration

The issue is that the original terminal pages to be migrated are not deleted after the migration, so, as a result of the migration we have the new nested pages (that are created under their corresponding parents) along with the original termina pages.

Steps to reproduce

• On a fresh xwiki instance (version 14.10.3) install "Nested Pages Migrator Application" version 0.9.0
• On the "Nested Pages Migration" application create a new project
• On the project home page start the migration of a space named "TEST" using this configuration
  Note that the TEST space is composed of 3 terminal pages : Page1, Page2, and Page3 which have these parent/child relationships : Page1 is the parent of Page2 and Page2 is the parent of Page3. Here is the XAR used for the test : TEST.WebHome.xar.
• Click on the Compute Plan button, see the screenshot of the results :
  
• After that click on the Execute Plan button to execute the migration

Expected results : The migration is executed successfully and the pages have been moved under their corresponding parent pages, so, we should now have the following document tree : TEST>Page1>Page2>Page3.

Actual results : The migration is executed successfully but we have a duplication of pages, see screenshot :