scan.py: replace forgotten call to print() by logger.info()

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
Frontend: always make sure scan worflow drawers know to which canvas they belong

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
Frontend: Multiscan: keep trying to fix this thing

Signed-off-by: Jerome Flesch <jflesch@gmail.com>