[atomic] Update on Kubernetes and Fedora Atomic 25

[Josh Berkus <jberkus redhat com>]

**TL;DR**: If you are a production user of Kubernetes on Fedora Atomic
Host, you can now upgrade to Fedora Atomic Host 25.  Kubernetes 1.4 is
part of the base image now.

Per our previous announcement, we wanted to make a change to Fedora
Atomic Host, and in concert with the Kubernetes community move to an
entirely containerized install of Kubernetes, which would make it easier
for users to choose their Kubernetes version or distribution.  However,
some of the upstream technical issues with that change will take longer
than we expected to resolve.  As such, we have added Kubernetes and
Flannel back into the base image for Fedora Atomic 25, as of today's OStree.

If you are a production user of Fedora Atomic 24 with Kubernetes, you
may now rebase and upgrade.  Please make sure to go directly to the
2016-12-21 or later OSTree image, skipping any earlier ones for version 25.

Do note that the version of Kubernetes which ships with
version 25 is Kubernetes 1.4.6.  As such, you should test to make sure
no incompatibilities have been introduced by the Kubernetes upgrade
before rebasing production servers.  While the goal of the Kubernetes
project it to maintain complete backwards compatibility, there may be
minor exceptions, especially for specific addons.

At this point, we plan to transition to containerized Kubernetes for
Fedora Atomic Host 26, in mid-2017.  At that point, we expect the bugs
to be worked out, and will be providing a migration guide.  If you can
help with testing and feedback, please  comment on this mailing list.

Users of Fedora Atomic Host who do not use Kubernetes or Flannel will be
largely unaffected by these changes.

-- 
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Josh Berkus
Project Atomic
Red Hat OSAS