Improve docker rmi, keeping all base images
Improve docker rmi, keeping all base images

Signed-off-by: Stefan Scherer <2fe843265e65a9540d5df64f4bed2ee6b7ca283e@icloud.com>

StefanScherer/dockerfiles-windows,StefanScherer/dockerfiles-windows,StefanScherer/dockerfiles-windows,StefanScherer/dockerfiles-windows,StefanScherer/dockerfiles-windows,StefanScherer/dockerfiles-windows,StefanScherer/dockerfiles-windows