Fog::Image::OpenStack does not correctly construct URL for versioned API

[plribeiro3000]

trafficstars

My image endpoint is configured as http://glance.local:9292/ without an API version number, so Fog::Image::OpenStack uses Fog::OpenStack.get_supported_version to figure out the versioned API base URL by querying GET / on the Glance. This is the result returned from Glance (Kilo):

{
    "versions": [
        // various entries for v2.x omitted for brevity
        {
            "id": "v1.1",
            "links": [
                {
                    "href": "http://glance.local:9292/v1/",
                    "rel": "self"
                }
            ],
            "status": "SUPPORTED"
        },
        {
            "id": "v1.0",
            "links": [
                {
                    "href": "http://glance.local:9292/v1/",
                    "rel": "self"
                }
            ],
            "status": "SUPPORTED"
        }
    ]
}

The get_supported_version method decides that it likes the v1.1 version and returns that, but then Fog::Image::OpenSTack constructs the wrong URL in lib/fog/openstack/image.rb:206

@path = "/" + Fog::OpenStack.get_supported_version(SUPPORTED_VERSIONS,
                                                   uri,
                                                   @auth_token,
                                                   @connection_options)

This breaks because the URL path is /v1/ for the v1.1 API, not /v1.1/. Glance reports the correct URL in the response shown above, and that URL should be preferred over doing our own guesswork.

Original issue opened by @majewsky at fog/fog#3578

[plribeiro3000]

cc/ @majewsky @TerryHowe @tealover