New virtualmin-base packages for RHEL/CentOS and Fedora

I've rolled new virtualmin-base as well as ClamAV packages into the software repository to address a number of installation issues that folks have reported over the past few days. I've you've had problems installing on any Red Hat-based system, please give it another try and if the problem(s) persist, file a bug or a customer issue.

Specifically, this addresses the ClamAV signature errors on x86_64 platforms, and the postfix::set_current_value error during installation of virtualmin-base.