Description of problem:
The download URL published for each unit includes the hostname. So, when the parent node's hostname is changed, repositories need to be (node) published.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Setup parent and child node.
2. (node) Publish a repository.
3. Sync the child.
Get 404 downloading files associated with content units (rpms).
Should just work.
Moved to https://pulp.plan.io/issues/212