Private temp files are still accessible to anonymous users.

Problem/Motivation

Even when a managed file element's #uri_scheme is set to private the temp file is available to anonymous user

Steps to reproduce

• As an anonymous user
• Goto /form/test-element-managed-file
• Upload a text file
• Click link to temp file

Proposed resolution

Block anonymous users from accessing temporary private files.

Remaining tasks

• Remove links from file upload widget to anonymous file
• Block access to anonymous file.
• Write tests