Unable to save Admin system permissions #834

• BookStack Version: .22-dev
• PHP Version: 7.0.30
• MySQL Version: 5.6

When I edit the admin role and deselect 'Manage permissions on own book, chapter & pages' and click 'Save', I would expect that setting to remain deselected.

When I edit the admin role and deselect 'Manage permissions on own book, chapter & pages' under system permissions' for the role and click 'save', it is not saved after I edit the role again to double check it.

GOAL:
What I am trying to accomplish is having private books for users that members of the admin group cannot see.

*Steps to reproduce

1. Edit the admin role
2. deselect 'Manage permissions on own book, chapter & pages'
3. click 'save'
4. edit the admin role
5. check if settings were saved.