fix SetFolderWriteTime: Season Folder not being updated

@markus101

Thanks for merging in my changes.
However, it's not setting the write time on the season folder.

My understanding is that ```episodeFile.Path``` contains the path to the original location of the file.
By the time SetFolderWriteTime is called for the season folder, I don't see where ```episodeFile.Path``` gets updated.
So I think it would be more appropriate to get the seasonFolder from ```destinationFileName```