[cern] Upgrade to Fedora Atomic 25

Cherry-pick: https://review.openstack.org/#/c/417457/8

Image contains: kubernetes-1.4.7-1.fc25.x86_64 docker-1.12.5-4.git03508cc.fc25.x86_64 flannel-0.5.5-8.fc25.x86_64 etcd-3.0.15-1.fc25.x86_64

• For this upgrade the upstream image is used, which is uploaded here [1].
• Minor changes for flannel and docker-storage-setup were needed.
• The image will be built in the CI and uploaded to tarballs.openstack.org as soon as possible.

[1] https://fedorapeople.org/groups/magnum/fedora-atomic-25-20161221.qcow2

Change-Id: Iac6e30c530821a49a5c3978e335e0b1d56a576e0

Conflicts: magnum/drivers/common/templates/fragments/configure_docker_storage_driver_atomic.sh magnum/drivers/common/templates/kubernetes/fragments/write-network-config.sh magnum/drivers/k8s_fedora_atomic_v1/version.py magnum/drivers/swarm_fedora_atomic_v1/version.py magnum/tests/contrib/gate_hook.sh