converter: use OpenWriter helper function

When several goroutines call uncompress converter in parallel, the ref name
conflicts each other. This leads to Writer method failing with Unavaliable error
without retry.
For solving this issue, OpenWriter helper should be used. This allows them to
retry in such situations.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

images/converter/uncompress/uncompress.go

@@ -55,7 +55,7 @@ func LayerConvertFunc(ctx context.Context, cs content.Store, desc ocispec.Descri
 	}
 	defer newR.Close()
 	ref := fmt.Sprintf("convert-uncompress-from-%s", desc.Digest)
-	w, err := cs.Writer(ctx, content.WithRef(ref))
+	w, err := content.OpenWriter(ctx, cs, content.WithRef(ref))
 	if err != nil {
 		return nil, err
 	}