Use constants so we won't have to edit a dozen places in the test when
the package versions are bumped.
Also switch to using Fedora 31 GPG key now that it has branched for
Fedora 30.
there's 7.2 in Fedora 29 (which we use in Jenkins) and 7.3 in
Rawhide which causes test jobs to fail with unsolved dependencies.
Alternatively we can switch to another recipe for cloud image tests.
This adds support for the optional blueprint section [customizations].
Use it like this:
[customizations]
hostname = yourhostnamehere
[[customiations.sshkey]]
user = root
key = root user key
Change versions to match Fedora versions. Add version numbers to the
blueprints except for glusterfs.toml, not having a version is used as
part of the tests.
