Signed-off-by: mooncake <xcoder@tenxcloud.com>

* Adds support for Multus (multiple interfaces) CNI plugin

Multus is a latin word for "Multi". As the name suggests, it acts as a
Multi plugin in Kubernetes and provides multiple network interface
support in a pod. Multus uses the concept of invoking delegates by
grouping multiple plugins into delegates and invoking them in the
sequential order of the CNI configuration file provided in json format.

* Change CNI version (0.1.0->0.3.1) of Contiv to be compatible with Multus

When using resolvconf_mode host_resolvconf, there is an early DNS
config stage where Kubernetes cluster DNS is not injected for host
DNS intially. Later, the cluster DNS is enabled, but we do not
need to run every task from the kubernetes/preinstall role.

* Added the missing environment for proxy for get_url

* Update upgrade.yml

* Fixed spaces

* Fixed spaces

* Update upgrade.yml

Upstream Changes:

   - coredns v1.2.5 (https://github.com/coredns/coredns/releases/tag/v1.2.5)

NOTE:

   - Switch image repo to https://hub.docker.com/r/coredns/coredns/ (https://github.com/kubernetes-incubator/kubespray/pull/3595#issuecomment-433962973)

Standalone etcd nodes do not generate node-$hostname certs and do
not need this serial calculated.

fix modify the way of the command 'yum remove xxx', e.g. docker-selinux and docker-engine-selinux packages

This reverts commit 8ba6b601.

* do it like in kubernetes/secrets

* fix indentation

* processed comments

* missed one, sorry

* trailing space fix

need set hostname by kubeadm

Upstream Changes:

-   ingress-nginx 0.20.0 (https://github.com/kubernetes/ingress-nginx/releases/tag/nginx-0.20.0)

Our Changes:

-   Sync templates with upstream changes

kubeadm sets node label node-role.kubernetes.io/master=''
and this is not configurable. We should use it everywhere.

* codestyle tests

* Download destination can be different than local_release_dir

kube-router v0.2.1 highlights from changelog:
- IPv6 WIP but pretty close to full working functionality
- fully support network policy semantics with addition of support for
  ipblock and except

* warning on meta flush_handlers

* avoid rm

* avoid "Module remote_tmp /root/.ansible/tmp did not exist and was created with a mode of 0700, this may cause issues when running as another user. To avoid this, create the remote_tmp dir with the correct permissions manually" warning on subsequent tasks using blockinfile

* is match

* failed

* version_compare

* succeeded

* skipped

* success

* version_compare becomes version since ansible 2.5

* ansible minimal version updated in doc and spec

* last version_compare

* [jjo] add kube-router support

Fixes cloudnativelabs/kube-router#147.

* add kube-router as another network_plugin choice
* support most used kube-router flags via
  `kube_router_foo` vars as other plugins
* implement replacing kube-proxy (--run-service-proxy=true) via
  `kube_proxy_mode: none`, verified in a _non kubeadm_enabled_
  install, should also work for recent kubeadm releases via
  `skipKubeProxyInstall: true` config

* [jjo] address PR#3339 review from @woopstar

* add busybox image used by kube-router to downloads

* fix busybox download groups key

* rework kubeadm_enabled + kube_router_run_service_proxy

- verify it working ok w/the kubeadm_enabled and
  kube_router_run_service_proxy true or false

- introduce `kube_proxy_remove` fact, to decouple logic
  from kube_proxy_mode (which affects kubeadm configmap
  settings, thus no-good to ab-use it to 'none')

* improve kube-router.md re: kubeadm_enabled and kube_router_run_service_proxy

* address @woopstar latest review

* add inventory/sample/group_vars/k8s-cluster/k8s-net-kube-router.yml

* fix kube_router_run_service_proxy conditional for kube-proxy removal

* fix kube_proxy_remove fact (w/ |bool), add some needed kube-proxy tags on my and existing changes

* update kube-router tolerations for 1.12 compatibility

* add PriorityClass to kube-router DaemonSet

The hosts(5) manpage clearly states that the first entry is the
"canonical name", or FQDN (Fully-Qualified Domain Name):

    IP_address canonical_hostname [aliases...]

By using the alias as a first entry, `hostname -f` does not return the
correct domain which breaks all sorts of unrelated functionality (it
has impact over email server configuration, for example).