Update Fedora cloud image to its latest version

Latest Fedora cloud images are available here

  http://cloud.fedoraproject.org/

With this change, when a Fedora version comes up,
d-i-b will point to it automatically.

Fixes 1199237

(Also, thanks to Lucas Gomes for testing.)

Change-Id: Ifcb8a48f3baf3ef841f00e6a20c6fd9f79fea129
Merge "Update Fedora cloud image to its latest version"