A few things have changed and we need to fix them in one go.
Use mirror for installing docker for buildset-registry
While, we need to make this more systemic, that's hanging off of the
mirror rework. For now, since we know all of these jobs are debian
based, just set the mirror location.
Replace use of zuul cloner with git clones
You can never be a prophet in your own hometown. This is now broken
because of the git cache rework, so just replace it.
Update libjemalloc library
python:slim is based on buster now, which has libjemalloc2 not
libjemalloc1.
Remove gerrit repo remote for submodules
A recent change to the base jobs to use prepare-workspace-git
broke the gerrit image builds by actually having the origin
remote by /dev/null as intended. This breaks submodules because
for a few of them where we don't have matching stable branches
the submodule relative path behavior is actually exactly what
we want.
Since we don't care about the remote otherwise, remove the
origin remote before doing the submodule update --init so that
the submodule will clone the refs from the zuul prepared repo.
Change-Id: Ieb5b6bc8711fe971ed3445c7c267306ac4616464
9ab25e89a9