Update vendor files to point to kubernetes-1.12.0-beta.1

vendor/k8s.io/client-go/discovery/round_tripper.go

@@ -14,13 +14,13 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-// Package transport provides a round tripper capable of caching HTTP responses.
 package discovery
 
 import (
 	"net/http"
 	"path/filepath"
 
+	"github.com/golang/glog"
 	"github.com/gregjones/httpcache"
 	"github.com/gregjones/httpcache/diskcache"
 	"github.com/peterbourgon/diskv"
@@ -48,4 +48,15 @@ func (rt *cacheRoundTripper) RoundTrip(req *http.Request) (*http.Response, error
 	return rt.rt.RoundTrip(req)
 }
 
+func (rt *cacheRoundTripper) CancelRequest(req *http.Request) {
+	type canceler interface {
+		CancelRequest(*http.Request)
+	}
+	if cr, ok := rt.rt.Transport.(canceler); ok {
+		cr.CancelRequest(req)
+	} else {
+		glog.Errorf("CancelRequest not implemented by %T", rt.rt.Transport)
+	}
+}
+
 func (rt *cacheRoundTripper) WrappedRoundTripper() http.RoundTripper { return rt.rt.Transport }