Add toleration to CSI nodeplugin

This commit allows the CSI nodeplugin to start on machines with taints.
A use case is nodegroups; a dedicated machine (e.g. ASICs and GPU) will
join the cluster with a pre-defined taint so that pods can't grab
valuable resources. However the taint currently stops the node from
starting the plugin and getting a node ID, so we cannot use cinder
volumes within pods.

This commit ports the work done by jichenjc
(kubernetes/cloud-provider-openstack#1276) into
Magnum fixing the issue here too.

Story: 2007048
Task: 42097

Change-Id: I8dec787660604d52156d71617d2bdda73fb62e9c

Author: DavidFair

magnum/drivers/common/templates/kubernetes/fragments/enable-cinder-csi.sh

@@ -391,6 +391,8 @@ spec:
       labels:
         app: csi-cinder-nodeplugin
     spec:
+      tolerations:
+        - operator: Exists
       serviceAccount: csi-cinder-node-sa
       hostNetwork: true
       containers: