Fixed a bug that caused disks to fail to be mounted to a multi-zone Kubernetes clusters

• The multi-zone Kubernetes clusters created on or after January 28, 2019 are unaffected by this bug.
• For any multi-zone Kubernetes cluster created before January 28, 2019, ACK offers a solution to this bug that allows you to mount a disk to the cluster. For more information, see Mount a disk to a Kubernetes cluster node.