registry: newV1Endpoint: make it clear we skip validation for Docker Hub

validateEndpoint uses `v1Endpoint.ping` to verify if the search API can
use a secure connection, and to fall back to basic auth. For Docker Hub,
we don't allow insecure connections, and `v1Endpoint.ping` will not connect
to Docker Hub (Docker Hub also does not implement the `_ping` endpoint,
so doing so would always fail).

Let's make it more clear that we don't do any validation, and return
early.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

registry/search_endpoint_v1.go

@@ -42,6 +42,12 @@ func newV1Endpoint(index *registry.IndexInfo, headers http.Header) (*v1Endpoint,
 		return nil, err
 	}
 
+	if endpoint.String() == IndexServer {
+		// Skip the check, we know this one is valid
+		// (and we never want to fall back to http in case of error)
+		return endpoint, nil
+	}
+
 	err = validateEndpoint(endpoint)
 	if err != nil {
 		return nil, err