Support the infra server's /version endpoint in the automate-deployed infra server

[yzl]

🔩 Description: What code changed, and why?

Supporting the infra server's /version endpoint enables using knife ec backup to backup the data from an infra server installed from an omnibus package and using knife ec restore to restore the data to an automate-deployed infra server.

Fixes #3301

⛓️ Related Resources

👍 Definition of Done

👟 How to Build and Test the Change

Deploy an infra server and take a backup

1. In automate/components/automate-deployment, run vagrant up to bring up a minimal vagrant box. Use vagrant ssh to login, and go to the `/a2/ directory.
2. Install a standalone infra server.
3. As root, install chefdk (dpkg -i chefdk_4.7.113-1_amd64.deb) and the knife-ec-backup plugin (apt-get install ruby-dev g++ libpq-dev; chef gem install knife-ec-backup).
4. As root, run knife fetch ssl to make the infra server's SSL certs available to knife.
5. As root, backup the infra server: mkdir ./tmp; knife ec backup --server-url https://automate-deployment.test --key <admin-key> ./tmp. The backup will land in automate/components/automate-deployment/tmp.
6. Exit the vagrant box and run vagrant destroy -f to stop and remove it.

Deploy the infra server using Automate and restore the data from the first infra serveer

1. Checkout the branch yzl/3301 from the automate repo, bring up the studio dev environment, and run build components/automate-load-balancer.
2. In automate/components/automate-deployment, run vagrant up to bring up a minimal vagrant environment.
3. Go to the /a2 directory and, as root, install automate and infra server using the package built in the first step, e.g. ./components/automate-deployment/bin/linux/chef-automate deploy --product automate --product chef-server --hartifacts ./results --override-origin <your-origin>
4. As root, install chefdk (dpkg -i chefdk_4.7.113-1_amd64.deb) and the knife-ec-backup plugin (apt-get install ruby-dev g++ libpq-dev; chef gem install knife-ec-backup).
5. As root, run knife ssl fetch to make Automate's SSL certs available to knife.
6. As root, go to components/automate-deployment/tmp, which contains the infra server backup, and restore the data to the infra server:

knife ec restore . -u pivotal --webui-key /hab/svc/automate-cs-oc-erchef/data/webui_priv.pem --skip-version-check -s https://`hostname -f`

✅ Checklist

• I have read the CONTRIBUTING document.
• Tests added/updated?
• Docs added/updated?
• All commits have been signed-off for the Developer Certification of Origin.

📷 Screenshots, if applicable

[chef-davin]

Thanks for putting in this PR so quickly! It'll definitely help when it gets merged.