Tests various non-default configuration:

* Custom users
* Network interfaces, VLANs, bridges, bonds
* Software RAID
* LVM & docker devicemapper
* timezone
* Package mirrors
* yum-cron / DNF automatic

This improved test coverage allows us to be more confident about these
features working on CentOS 8.

Change-Id: I36148e4356deb7d5ec00d8d3ebeb2d3932ff4f94
Story: 2006574
Task: 38938