vendor containers/image for parallel copying of layers

Vendor the latest containers/image 50e5e55e46a391df8fce1291b2337f1af879b822
to enable parallel copying of layers.

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

vendor/golang.org/x/sys/unix/dev_freebsd.go

@@ -1,30 +0,0 @@
-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Functions to access/create device major and minor numbers matching the
-// encoding used in FreeBSD's sys/types.h header.
-//
-// The information below is extracted and adapted from sys/types.h:
-//
-// Minor gives a cookie instead of an index since in order to avoid changing the
-// meanings of bits 0-15 or wasting time and space shifting bits 16-31 for
-// devices that don't use them.
-
-package unix
-
-// Major returns the major component of a FreeBSD device number.
-func Major(dev uint64) uint32 {
-	return uint32((dev >> 8) & 0xff)
-}
-
-// Minor returns the minor component of a FreeBSD device number.
-func Minor(dev uint64) uint32 {
-	return uint32(dev & 0xffff00ff)
-}
-
-// Mkdev returns a FreeBSD device number generated from the given major and
-// minor components.
-func Mkdev(major, minor uint32) uint64 {
-	return (uint64(major) << 8) | uint64(minor)
-}