modify cluster create help

Magnum cluster-create help shows cluster-template asn an optional arguments but seems like it is a required parameter.

root@node1:~/devstack$ magnum help cluster-create

usage: magnum cluster-create [--name <name>] --cluster-template
                             <cluster_template> [--node-count <node-count>]
                             [--master-count <master-count>]
                             [--discovery-url <discovery-url>]
                             [--timeout <timeout>]

Create a cluster.

Optional arguments:
  --name <name> Name of the cluster to create.
  --cluster-template <cluster_template>
                        ID or name of the cluster template.
  --node-count <node-count>
                        The cluster node count.
  --master-count <master-count>
                        The number of master nodes for the cluster.
  --discovery-url <discovery-url>
                        Specifies custom discovery url for node discovery.
  --timeout <timeout> The timeout for cluster creation in minutes. The
                        default is 60 minutes.

root@node1:~/devstack$ magnum cluster-create --name=test
usage: magnum cluster-create [--name <name>] --cluster-template
                             <cluster_template> [--node-count <node-count>]
                             [--master-count <master-count>]
                             [--discovery-url <discovery-url>]
                             [--timeout <timeout>]
error: argument --cluster-template is required

I propose to modify the help option and move cluster-template to positional arguments.