Adds support for Multus (multiple interfaces) CNI plugin (#3166)

* Adds support for Multus (multiple interfaces) CNI plugin

Multus is a latin word for "Multi". As the name suggests, it acts as a
Multi plugin in Kubernetes and provides multiple network interface
support in a pod. Multus uses the concept of invoking delegates by
grouping multiple plugins into delegates and invoking them in the
sequential order of the CNI configuration file provided in json format.

* Change CNI version (0.1.0->0.3.1) of Contiv to be compatible with Multus

roles/network_plugin/multus/tasks/main.yml

@@ -0,0 +1,19 @@
+---
+- name: Multus | Copy manifest files
+  copy:
+    src: "{{ item.file }}"
+    dest: "{{ kube_config_dir }}"
+  with_items:
+    - {name: multus-crd, file: multus-crd.yml, type: customresourcedefinition}
+    - {name: multus-serviceaccount, file: multus-serviceaccount.yml, type: serviceaccount}
+    - {name: multus-clusterrole, file: multus-clusterrole.yml, type: clusterrole}
+    - {name: multus-clusterrolebinding, file: multus-clusterrolebinding.yml, type: clusterrolebinding}
+  register: multus_manifest_1
+
+- name: Multus | Copy manifest templates
+  template:
+    src: "{{ item.file }}.j2"
+    dest: "{{ kube_config_dir }}/{{ item.file }}"
+  with_items:
+    - {name: multus-daemonset, file: multus-daemonset.yml, type: daemonset}
+  register: multus_manifest_2