This prevents unexpected breakage on new Fedora release.
Fedora 20 is the last release known to work. Images based on Fedora 21
are currently broken as they lack required packages such as iproute.
Support for Fedora 21 is on the way and will follow soon once all images
have been verified.
Change-Id: I849732147302eaf00d864d6b5093ff6ac006f496