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/blobs.go

@@ -1,13 +1,13 @@
 package distribution
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
 	"net/http"
 	"time"
 
-	"github.com/docker/distribution/context"
 	"github.com/docker/distribution/reference"
 	"github.com/opencontainers/go-digest"
 )