Remove trailing slash from folderUrl, too, when comparing to
the file's url (minus file name minus trailing slash). FolderUrls
like file:///home/user/Desktop/ may appear and fail comparing.

Fixes regression introduced in 07001277a8a0893aeb54240d7f5cdd9825fb57ed
(see https://phabricator.kde.org/D10729) which fixes urls like
file:///home/user/foo (if using a different folder than Desktop)
but breaks moving files from one screen to another using normal
Desktop folder.

1. Use folder view, Desktop folder, more than one screen.

Create files and folders in Desktop folder and move them from one
screen to another. The Copy/Move/Link menu must not appear
and files/folders must be dropped onto the other screen.

2. Use a different folder than Desktop (the same on both screens).

Moving files/folders to another screen must work like in 1.