[jjo] add kube-router support (#3339)

* [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

roles/kubernetes/node/tasks/main.yml

@@ -146,15 +146,26 @@
   template:
     src: manifests/kube-proxy.manifest.j2
     dest: "{{ kube_manifest_dir }}/kube-proxy.manifest"
-  when: not kubeadm_enabled
+  when:
+    - not (kubeadm_enabled or kube_proxy_remove)
   tags:
     - kube-proxy
 
-- name: Purge proxy manifest for kubeadm
+- name: Purge proxy manifest for kubeadm or if proxy services being provided by other means, e.g. network_plugin
   file:
     path: "{{ kube_manifest_dir }}/kube-proxy.manifest"
     state: absent
-  when: kubeadm_enabled
+  when:
+    - kubeadm_enabled or kube_proxy_remove
+  tags:
+    - kube-proxy
+
+- name: Cleanup kube-proxy leftovers from node
+  command: "{{ docker_bin_dir }}/docker run --rm --privileged -v /lib/modules:/lib/modules --net=host {{ hyperkube_image_repo }}:{{ hyperkube_image_tag }} kube-proxy --cleanup"
+  when:
+    - kube_proxy_remove
+  # `kube-proxy --cleanup`, being Ok as per shown WARNING, still returns 255 from above run (?)
+  ignore_errors: true
   tags:
     - kube-proxy