jenkins: Unstuck buster-swh image build
Currently, due to a recent change to add a new dependency, we had to rebuild the docker image. The build  is stuck for unrelated reasons.
Which results in a poor coverage from for example this diff .
Somehow, we cannot retrieve the cassandra release keys from download.apache.org. The curl query is stuck from our networks.
Idea from @vsellier: using a mirror of it.
Migrated from T4615 (view on Phabricator)