Fix docker image ls output (#2000)

[dougszumski]

Backport from 2025.1

[gemini-code-assist]

Code Review

This pull request improves the reliability of fetching Docker image lists by using the --format option, which is a good change. However, the script does not correctly adapt the parsing of this new output format, leading to a potential bug when processing image names with port numbers in their repository. I've left a specific comment with details on how to fix this to make the change complete and robust.

[gemini-code-assist]

Using --format is a great improvement for robustness. However, this change is incomplete as it doesn't update the logic that parses the command's output. The parsing on line 34 is now incorrect and will fail for image names that include a port in the registry name (e.g., my.registry:5000/image:tag) due to the cut -f 1,2 -d: command.

To complete this fix, please also update line 34 in this PR. It should be simplified to:

images=$(cat "$output_file")

This will correctly read the image names that are already formatted by the docker image ls command. Note that on line 34, $1-scanned-container-images.txt should also be replaced with $output_file for consistency.