Use python 3.11-alpine image in catalog-be backend-init

Use python 3.11-alpine image in catalog-be backend-init

- use public python:3.11-alpine image [0]
- remove unused packages from the image (lib-xml,-ffi,libressl,...)
- simplify dockerfile syntax a bit
- make sure import_normatives.sh doesn't fail silently
  (which makes root cause analysis harder)

[0] official images are regularly updated and make it easier to
    reason what they contain (as opposed to custom images)

Issue-ID: SDC-4803
Change-Id: Id2676b4e92298a0823da35dd601a1991b9e93400
Signed-off-by: Fiete Ostkamp <fiete.ostkamp@telekom.de>