Update alpine images to alpine 3.9
What does this MR do?
Updates our alpine-based Docker images to use Alpine 3.9 (released at 2019-01-29).
Why was this MR needed?
The new stable version is out. Let's be up-to-date then
Are there points in the code the reviewer needs to double check?
Does this MR meet the acceptance criteria?
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Documentation created/updated -
Added tests for this feature/bug -
In case of conflicts with master- branch was rebased