Content/Read limitation by Location prevents the user from accessing the /admin page - the system checks the root location which can't be limited.

Current state:
After trying to access /admin page, the exception is thrown:

User does not have access to 'read' 'content' with: locationId '1'

Expected:
User is able to access the /admin page.

Steps to reproduce:
> Clean eZ Platform v2.5.1 installation
> Add Role Foo
> Assign policies to the role:

• User/Login SiteAccess: Admin
• Content/Read Location: /eZ Platform

> Create new user and assign him to the Foo role
> Login as the new user
The exception should appear after redirection to the /admin page.

This is caused by ezsystems/ezplatform-admin-ui/src/bundle/Controller/ContentViewController:supplyIsLocationInvisible which (in some cases) loads root's parentLocation.