Reordering pages in secondary language changes default slug

[rrelmy]

Describe the bug
In a site with english as default locale and german as secondary locale, havin german (secondary locale) selected on the pages tree and reorder the pages will change the slugs in the default locale (english) to the ones from the selected locale.

To Reproduce
Steps to reproduce the behavior:

1. Go to pages overview
2. Select a locale other than the default locale
3. Start reordering the pages
4. Save the changes
5. Check the slugs on the primary locale

Expected behavior
Reordering pages should never change the slug of a page!

Environment details (please complete the following information):

• Statamic Version: 2.11.21
• Fresh Install or Upgrade: Updated several times
• OS: 18.04
• Browser: Chrome
• Web Server: Nginx
• PHP Version: 7.2
• Addons installed: Spock, and other unrelated addons

Additional context
I can not reproduce the issue in v3 :-)