Initial version of Flannel using CNI (#1486)

* Updates Controller Manager/Kubelet with Flannel's required configuration for CNI
* Removes old Flannel installation
* Install CNI enabled Flannel DaemonSet/ConfigMap/CNI bins and config (with portmap plugin) on host
* Uses RBAC if enabled
* Fixed an issue that could occur if br_netfilter is not a module and net.bridge.bridge-nf-call-iptables sysctl was not set

roles/network_plugin/flannel/tasks/pre-upgrade.yml

@@ -0,0 +1,19 @@
+---
+- name: Flannel pre-upgrade | Purge legacy flannel systemd unit file
+  file:
+    path: "/etc/systemd/system/docker.service.d/flannel-options.conf"
+    state: absent
+  notify:
+    - Flannel | delete default docker bridge
+
+- name: Flannel pre-upgrade | Purge legacy Flannel static pod manifest
+  file:
+    path: "{{ kube_manifest_dir }}/flannel-pod.manifest"
+    state: absent
+  notify:
+    - Flannel | delete flannel interface
+
+- name: Flannel pre-upgrade | Remove Flannel's certificate directory not required by CNI
+  file:
+    dest: "{{ flannel_cert_dir }}"
+    state: absent