ci: Use the docker image id instead of ':latest' tag in jobs
This avoids a potential race condition when multiple pipelines are running in parallel and could update/overwrite the ':latest' tag.
For example, with two pipelines, A and B, the following could occur:
A1 -> build image and update :latest tag to id ImageA B1 -> build image and update :latest tag to id ImageB A2 -> use image from :latest tag assuming it's ImageA, but it's actually ImageB ...
Explicitly using the image id avoids the problem:
A1 -> build image with id ImageA and update :latest tag B1 -> build image with id ImageB and update :latest tag A2 -> use image with id ImageA B2 -> use image with id ImageB ...
Signed-off-by: Alexandros Frantzis alexandros.frantzis@collabora.com