Geo: Enable fast SSH key lookup and install git-lfs

As part of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/7791, we need to ensure that SSH keys are available for both primary and secondary Geo nodes. In order to do this, we need to enable https://docs.gitlab.com/ee/administration/operations/fast_ssh_key_lookup.html. For various reasons this cannot be done by default in the omnibus installer / default Docker images so it needs to be done here.

Also, upcoming Geo QA tests will also require git-lfs to be installed, which this MR also includes commands for.