Also fix yaml lint issues

Fixes #1703

* Leave all.yml to keep only optional vars
* Store groups' specific vars by existing group names
* Fix optional vars casted as mandatory (add default())
* Fix missing defaults for an optional IP var
* Relink group_vars for terraform to reflect changes

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>

Also place in global vars and do not repeat the kube_*_config_dir
and kube_namespace vars for better code maintainability and UX.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

In order to enable offline/intranet installation cases:
* Move DNS/resolvconf configuration to preinstall role. Remove
  skip_dnsmasq_k8s var as not needed anymore.

* Preconfigure DNS stack early, which may be the case when downloading
  artifacts from intranet repositories. Do not configure
  K8s DNS resolvers for hosts /etc/resolv.conf yet early (as they may be
  not existing).

* Reconfigure K8s DNS resolvers for hosts only after kubedns/dnsmasq
  was set up and before K8s apps to be created.

* Move docker install task to early stage as well and unbind it from the
  etcd role's specific install path. Fix external flannel dependency on
  docker role handlers. Also fix the docker restart handlers' steps
  ordering to match the expected sequence (the socket then the service).

* Add default resolver fact, which is
  the cloud provider specific and remove hardcoded GCE resolver.

* Reduce default ndots for hosts /etc/resolv.conf to 2. Multiple search
  domains combined with high ndots values lead to poor performance of
  DNS stack and make ansible workers to fail very often with the
  "Timeout (12s) waiting for privilege escalation prompt:" error.

* Update docs.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

* Don't push containers if not changed
* Do preinstall role only once and redistribute defaults to
  corresponding roles

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

Signed-off-by: Chad Swenson <chadswen@gmail.com>

Also adds all masters by hostname and localhost/127.0.0.1 to
apiserver SSL certificate.

Includes documentation update on how localhost loadbalancer works.

It's required for port forwarding.

New variable disable_ipv6_dns in kubernetes/preinstall.

etcd facts are generated in kubernetes/preinstall, so etcd nodes need
to be evaluated first before the rest of the deployment.

Moved several directory facts from kubernetes/node to
kubernetes/preinstall because they are not backward dependent.

Currently kubespray does not install kubernetes in a way that allows cinder volumes to be used. This commit provides the necessary cloud configuration file and configures kubelet and kube-apiserver to use it.

 Please enter the commit message for your changes. Lines starting

test travis with sudo=true instead of required