Update alpine images to 3.15.4

[simonswine]

What this PR does / why we need it:

This updates all references to alpine images to the latest released 3.15.4

It was released yesterday to address busybox CVE-2022-28391

Checklist

• Add an entry in the CHANGELOG.md about the changes.

[simonswine]

Command used:

git ls-files  '*[Dd]ockerfile*' | grep -v ^vendor/ | xargs sed -i "s/alpine:[a-z0-9\\.]*/alpine:3.15.4/g"

[slim-bean]

do we want to pin this to the .4? or should we just do 3.15?

[slim-bean]

I think it would be better to do 3.15 and then we would auto get the latest patch fixes

[simonswine]

I think it would be better to do 3.15 and then we would auto get the latest patch fixes

I don't think we want that. E.g if we would have built 3.15 let's say two weeks ago, how would we clearly understand that we are vulnerable to CVE-2022-28391 which was only released 2 days ago. I think we want immutable tags used as base image, so we clearly have our dependecies pinned down.