Use "set -xe" for exiting on errors

[kimwnasptd]

Refs canonical/bundle-kubeflow#1030

The current scanning action is failing because the bash script for gathering the image is failing, but the whole step is not failing
https://github.com/canonical/bundle-kubeflow/actions/runs/10482022617/job/29032456143#step:6:13

Error: open releases/1.9/stable/kubeflow/bundle.yaml: no such file or directory
Error: open releases/1.9/stable/kubeflow/bundle.yaml: no such file or directory
Image list:

This PR adds set -xe to all the bash scripts, to ensure they will exit if any of their sub-commands exits prematurely

[mvlassis]

The proposal looks good to me!