check-glance-store doesn't handle remote images

[omgjlk]

Some images are added with a remote location, so that they're fetched each time. The store checker doesn't take that into account and alerts for these images since they're not in the store. The checker should utilize the API to discover the location(s) of the image and only check the filesystem if it is supposed to be located there.

The location check will require allowing location data to be returned from the glance API.