Fix kube-proxy configuration for kubeadm (#3958)

- Creates and defaults an ansible variable for every configuration option in the `kubeproxy.config.k8s.io/v1alpha1` type spec
  - Fixes vars that were orphaned by removing non-kubeadm
  - Fixes previously harcoded kubeadm values
- Introduces a `main` directory for role default files per component (requires ansible 2.6.0+)
  - Split out just `kube-proxy.yml` in this first effort
- Removes the kube-proxy server field patch task

We should continue to pull out other components from `main.yml` into their own defaults files as I did here for `defaults/main/kube-proxy.yml`. I hope for and will need others to join me in this refactoring across the project until each component config template has a matching role defaults file, with shared defaults in `kubespray-defaults` or `downloads`

roles/kubernetes/kubeadm/tasks/main.yml

@@ -92,21 +92,6 @@
     - kubeadm_discovery_address != kube_apiserver_endpoint
   notify: restart kubelet
 
-- name: Update server field in kube-proxy kubeconfig
-  shell: >-
-    {{ bin_dir }}/kubectl --kubeconfig {{ kube_config_dir }}/admin.conf get configmap kube-proxy -n kube-system -o yaml
-    | sed 's#server:.*#server:\ {{ kube_apiserver_endpoint }}#g'
-    | {{ bin_dir }}/kubectl --kubeconfig {{ kube_config_dir }}/admin.conf replace -f -
-  delegate_to: "{{groups['kube-master']|first}}"
-  run_once: true
-  when:
-    - 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
   file:
@@ -116,18 +101,6 @@
     force: yes
   when: kube_network_plugin in ['calico','canal']
 
-- name: Restart all kube-proxy pods to ensure that they load the new configmap
-  shell: "{{ bin_dir }}/kubectl --kubeconfig {{ kube_config_dir }}/admin.conf delete pod -n kube-system -l k8s-app=kube-proxy"
-  delegate_to: "{{groups['kube-master']|first}}"
-  run_once: true
-  when:
-    - 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