fix import torrent

When using "File->Import existing torrent...", it will fail if you have "Options->Downloads->Keep incomplete torrents in:" selected and you do not select "Skip the data checking stage and start seeding immediately".

Also, even if you import the torrent successfully by selecting to skip the data check, if you later select for a "Force Recheck", the recheck will fail (because qBittorrent thinks the file is located somewhere else) and qBittorrent will attempt to download the file again.

This may not be the most correct way to implement this fix (I didn't dig to thoroughly into the code), but it *does* work.  Tested and it's what I'm currently running on my computer until this or an equivalent fix gets implemented. 

This should also at least partially solve #804