Can't generate usable fast ISOs when switching config flags such as ENABLE_GUI #100
Description
When generating fast ISOs, the DONOR_ISO's comps.xml is used. If you switch a configuration option that would alter the comps.xml, it is not pulled in and only the old groups are present.
This can be re-created by building a non-GUI ISO, then switching to a GUI build, and using the previously built non-GUI ISO as the DONOR_ISO. You will get an error at install time because Anaconda can't find the gnome-desktop group.
Per @marshalljmiller we should copy over a new comps.xml as part of the fast ISO generation.