Change URLs once again to a hash-specific reference.

(RawGit caches files permanently.)
First attempt at a Fedora Cloud image, based on
https://git.fedorahosted.org/cgit/spin-kickstarts.git/tree/fedora-cloud-base.ks?h=f21
Add missing `%end` on pre-install script
I got the Cloud server environment's name wrong
Abandon utility script, since it's not useful for a cloud-init instance
Go back to MBR, even for cloud image
Fix post-install scripts' debug output redirection
We really shouldn't remove authconfig.

The cloud base kickstart in Fedora 21's spin-kickstarts repository
removes authconfig with its requirements, but in doing so takes away
openssl CLI.
Merge branch 'feature/fedora-21' into develop
Update SHA hash references for raw kickstart file URLs