Bump RAWHIDE and DEVEL versions to 21

Don't pull rawhide into F20 images, and avoid unstable
livecd-tools in the /development branch.

Change-Id: If3fb81d66f9a6acf58d13df9eb28ef9bc2deea36
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1091693
Signed-off-by: Ryan Barry <rbarry@redhat.com>