core: Be more explicit about requiring version
core: more logging
Remove erroneous yum upgrade.

This upgrade shouldn't be part of the docker setup process. If an
upgrade is needed, it should be done independently of the docker setup.
Do it to your base image, or if needed, as a shell provisioner step.
Merge pull request #4431 from purpleidea/bug/remove-upgrade

guests/redhat: remove erroneous yum upgrade.
v1.6.4