fedora 21 releng-issued image

Image info available here:
http://koji.fedoraproject.org/koji/taskinfo?taskID=7978938

The gz tarball on this page contains the rootfs and metadata.

The xz tarball available at
lsm5/docker-brew-fedora@606897f6b35f4e77b4b386135128385018a7412c
only includes the rootfs.

Signed-off-by: Lokesh Mandvekar <lsm5@fedoraproject.org>

	modified:   library/fedora
Merge pull request #313 from lsm5/fedora-21-beta

fedora 21 releng-issued image