vendor: update everything

* If possible, update each dependency to the latest available version.

* Use releases over commit IDs and avoid vendoring branches.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/docker/distribution/registry/client/blob_writer.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -9,7 +10,6 @@ import (
 	"time"
 
 	"github.com/docker/distribution"
-	"github.com/docker/distribution/context"
 )
 
 type httpBlobUpload struct {