Description of problem:

The cachemanagement API is hardcoded to use v1:

  https://github.com/openstack/glance/blob/master/glance/api/middleware/cache_manage.py#L36

whereas if the v2 API is enabled, but not v1, this is problematic as clients would want to use v2 across the board.

Steps to Reproduce:
1. Install Glance
2. Disable v1 in *-paste.ini files
3. Call any url related to the cache middleware.
  
Actual results:

$ curl -H "X-Auth-Token: $tok" http://10.130.50.34:9292/v1/cached_images | python -m json.tool
  % Total % Received % Xferd Average Speed Time Time Time Current
                                 Dload Upload Total Spent Left Speed
100 119 100 119 0 0 25142 0 --:--:-- --:--:-- --:--:-- 29750
{
    "versions": [
        {
            "id": "v2.0",
            "links": [
                {
                    "href": "http://10.130.50.34:9292/v2/",
                    "rel": "self"
                }
            ],
            "status": "CURRENT"
        }
    ]
}


Expected results:

It should return the list of cached_images (if cache is enabled)