Can't create server_group in cli when 'policy' isn't specified

[wingwj]

'policy' param is a required param for in nova api. But it's a optional param in cli now and cli doesn't have one default value for it.

# nova help server-group-create
> usage: nova server-group-create [--policy <policy>] <name>

> Create a new server group with the specified details.

> Positional arguments:
> <name> Server group name.

> Optional arguments:
> --policy <policy> Policies for the server groups

Therefore, if you create a server_group without param specified using cli, a 'BadRequest' exception will be raised.

Here's the example:
# nova server-group-create wingwj
> ERROR (BadRequest): Invalid input received: 'policies' is either missing or empty. (HTTP 400) (Request-ID: req-49341cf1-41f5-4786-b825-2655bf1a8dfe)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/96382

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/96382
Committed: https://git.openstack.org/cgit/openstack/python-novaclient/commit/?id=376fd9f5bb825e2ce01fc9141c7477f25ac10101
Submitter: Jenkins
Branch: master

commit 376fd9f5bb825e2ce01fc9141c7477f25ac10101
Author: wingwj <email address hidden>
Date: Thu May 29 15:31:27 2014 +0800

    'policy' should be required in server_group_create

    The 'policies' param is a required param in nova api now.
    So, we also need to change it in cli.

    After the modification, the 'policy' param will be required now,
    and the old '--policy' style will still be available.

    Change-Id: I97921eef0f635c8d50a04bbdaf3ef4f1bfaa3e9d
    Closes-Bug: #1323909