Issue #21: Make rhel/opt repos mandatory and download anaconda-dracut

It is now mandatory to include an entry for a rhel repo and opt
repo in CONFIG_REPOS.  The user can change the path for these repos
but they both have to have a corresponding path and the script exits
if either repo is not assigned a path.  The opt repo is designated mandatory
because the rhel optional channel repo is used to pull in the anaconda-dracut
rpm (clip install will not complete without anaconda dracut module)