[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/kubeadm/tasks/main.yml

@@ -96,6 +96,9 @@
     - kubeadm_config_api_fqdn is not defined
     - is_kube_master
     - kubeadm_discovery_address != kube_apiserver_endpoint
+    - not kube_proxy_remove
+  tags:
+    - kube-proxy
 
 # FIXME(mattymo): Reconcile kubelet kubeconfig filename for both deploy modes
 - name: Symlink kubelet kubeconfig for calico/canal
@@ -114,3 +117,19 @@
     - kubeadm_config_api_fqdn is not defined
     - is_kube_master
     - kubeadm_discovery_address != kube_apiserver_endpoint
+    - not kube_proxy_remove
+  tags:
+    - kube-proxy
+
+# FIXME(jjo): need to post-remove kube-proxy until https://github.com/kubernetes/kubeadm/issues/776
+# is fixed
+- name: Delete kube-proxy daemonset if kube_proxy_remove set, e.g. kube_network_plugin providing proxy services
+  shell: "{{ bin_dir }}/kubectl delete daemonset -n kube-system kube-proxy"
+  delegate_to: "{{groups['kube-master']|first}}"
+  run_once: true
+  when:
+    - kube_proxy_remove
+    - is_kube_master
+    - kubeadm_discovery_address != kube_apiserver_endpoint
+  tags:
+    - kube-proxy