External files should not be copied during import

Problem/Motivation

The import of files with an external uri fails with the following message

> In FileSystem.php line 457:
> The specified file '/var/www/html/content/sync/[project]/files/https/[domain]/[file]' could not be copied because the destination directory 'https://[domain]' is not properly configured. This may be caused by a problem with file or directory permissions.