[vfs][addons] fix media view from addon given content

[AlwinEsch]

Description

Before was by opening of e.g. RAR file(s) the view on Videos, Music...
not shown.

Change only related to VFS addons in CFileDirectoryFactory, all
other formats not affected.

Inside compressed files seems a m_bIsFolder of CFile as true not to
handle the source from addon correct.

Motivation and Context

How Has This Been Tested?

This change is tested with old and reworked vfs.rar addon, vfs.sftp
and vfs.libarchive. There it has worked correct, further (as note)
becomes in reworked vfs.rar the directory support of rar files brought
back.

Screenshots (if appropriate):

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed