Adds an additional step so that VMs can access the package bucket
For https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/24539
This adds an extra step to the new storage template so that we can be sure that new Gitaly VMs have access to the package bucket for Omnibus installations. This access is not a hard-requirements, because we fall-back to packagecloud for installation but is something that should be done.