[TECHNICAL-SUPPORT] LPS-34437 Importing Site Templates with documents thumbnails and previews throws DuplicateFileException when user tries to overwrite existing template

https://issues.liferay.com/browse/LPS-34437

1. For "deleteThumbnail" getThumbnailFilePath returns a full path (containing the file name as well), so it makes sense to call that variable to "path" instead of "dirName".
2. For "deletePreviews": calling getPreviewFilePath with "null" as "type" returns a path (without the actual file names), that's why I chose "dirName" as variable name.

Regards,
Tibor