Description of problem:
If $uuid is used in a respod.d configuration file it is not respected under DNF (it works under yum).

Version-Release number of selected component (if applicable):
dnf-1.0.0-1.fc22

How reproducible:
Add $uuid to the configuration and run DNF

Steps to Reproduce:
1. Edit a configuration file, add $uuid to the mirrorlist or baseurl
2. Run DNF
3. Observe the access_log on the server side

Actual results:
No $uuid variable replacement is performed and the access logs on the server contain a literal $uuid string

Expected results:
The variable $uuid should be replaced with a unique ID by the DNF client such that the same ID appears on the server for each request from this client.

Additional info:
The man page for yum.conf states: "$uuid  This  will  be  replaced with a unique but persistent uuid for this machine.  The value that is first generated will be stored in /var/lib/yum/uuid and reused until this file is deleted."