When adding a source failed it wasn't being removed from the dnf object.
This fixes that, and returns an error when setting up the source fails.
Also adds a test for it.
This also includes detecting rawhide vs. non-rawhide releases and
adjusting the tests accordingly (some of the source names change).
This adds support for the optional blueprint section [customizations].
Use it like this:
[customizations]
hostname = yourhostnamehere
[[customiations.sshkey]]
user = root
key = root user key