image_rename() updated the Image object name and path before
computing the source paths for auxiliary files. As a result, the
auxiliary rename loop looked for files with the new image name,
while existing sidecars such as .roothash, .verity, and
.raw.tpmstate still used the old image name.
Delay updating the Image object until after renaming its settings
and auxiliary files. This lets image_auxiliary_path() resolve
existing sidecars from the old image name while
rename_auxiliary_file() assigns the new name.
Extend the import test raw image rename coverage to check
representative sidecars are renamed together with the image.