Clean up old docker images for deployer

[techietav]

After running the deployer 'build' and 'env apply' multiple times my server had run out of available disk space on the 100G root volume '/'.

I discovered a large number of docker images were present, but over 80G were not in use. This had used all available space on my 100G disk '/' as the images are mounted in /var/lib/containers. I removed all of these images using 'podman rmi' and ran the build again. Only 18G is being used on '/'

The deployer should remove previous build old images from the local docker instance when a new build is run and that way only have the current images present. Or there could be a 'clean' command to run before the build.