[discussion] Categorize Ansible tasks by eventual container

:construction: This is a pull request for discussion, not intended to be merged :construction: 

In preparation for #974, we're going through the Ansible playbooks to categorize each task based on where we eventually want each job to live: the CoreOS host itself or one of the containers. I'm doing this by adding a comment to each.

- [x] dev_web.yml
- [ ] prod_web.yml
- [ ] staging_web.yml
- [ ] jenkins_push.yml