Added generic CNI network plugin (#4322)

* Added generic CNI network plugin

* Added CNI network plugin documentation

* added necessary fix

roles/network_plugin/cni/tasks/main.yml

@@ -0,0 +1,13 @@
+- name: CNI | make sure /opt/cni/bin exists
+  file:
+    path: /opt/cni/bin
+    state: directory
+    mode: 0755
+    owner: root
+    group: root
+- name: CNI | Copy cni plugins
+  unarchive:
+    src: "{{ local_release_dir }}/cni-plugins-{{ image_arch }}-{{ cni_version }}.tgz"
+    dest: "/opt/cni/bin"
+    mode: 0755
+    remote_src: yes