Inconsistent "image" value on _get_image()

[huangtianhua]

1. Create a server from a image, then show the server details, the "image" is a dict, such as:
          {
                "id": image_id,
                "links": [{
                    "rel": "bookmark",
                    "href": bookmark,
                }],
            }

2. Create a server from a volume, then show the server details, the "image" is a dict, such as:
        ""

3. It's inconsistent "image" value, i think it's a bug.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/62807

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/62807
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=48a20d85cb9ef91c48f681c76fc6ca7512eccfbc
Submitter: Jenkins
Branch: master

commit 48a20d85cb9ef91c48f681c76fc6ca7512eccfbc
Author: huangtianhua <email address hidden>
Date: Wed Dec 18 12:19:31 2013 +0800

    Fix inconsistent "image" value on _get_image()

    The type of "image" value is different on showing details of a server,
    such as:
    1. It's a dict while creating a server from a image
    2. It's a empty string while creating a server from a volume

    We should modify the type to dict, otherwise someone who call
    the api will be confused about the value or can't parse the value
    in the same way.

    The patch just modifies the v3 api.

    Change-Id: I0d7ce59f64adec0933353af58dc5b5170390674b
    Closes-Bug: #1262039