CameraImportJob will copy RAW and JPEG, pass only the raws down to the
batch importer.

The batch importer then won't know about the associated file, and
extract the embedded file (or worse, make a development) of the RAW
file, schedule thumbnailing for that.

In the conclude step of the CameraImportJob, the files would be
associated, leading to the development being thrown away and run another
thumbnailing job.