add certmonger copr yum repo

This adds the yum repo for upstream to load the latest version of certmonger

/cc @jrafanie
Prefer: 

```
# repo to install the OS
url --url=http://mirror.centos.org/centos/6/os/x86_64/

# repos to install the packages found in the %packages section at appliance build time
# NOTE: copr repos have no release package. Add to wgets at line ~200
repo --name=extras --baseurl=http://mirror.centos.org/centos/6/extras/x86_64/
```