vendor in Update containers/image to add support for kpod save

This update allows the creation of docker-archive files when the
destination does not exists or is empty.  kpod save needs this functionality.

Signed-off-by: Dan Walsh <dwalsh@redhat.com>

vendor/github.com/containers/image/docker/archive/dest.go

@@ -19,15 +19,24 @@ func newImageDestination(ctx *types.SystemContext, ref archiveReference) (types.
 	if ref.destinationRef == nil {
 		return nil, errors.Errorf("docker-archive: destination reference not supplied (must be of form <path>:<reference:tag>)")
 	}
-	fh, err := os.OpenFile(ref.path, os.O_WRONLY|os.O_EXCL|os.O_CREATE, 0644)
+
+	// ref.path can be either a pipe or a regular file
+	// in the case of a pipe, we require that we can open it for write
+	// in the case of a regular file, we don't want to overwrite any pre-existing file
+	// so we check for Size() == 0 below (This is racy, but using O_EXCL would also be racy,
+	// only in a different way. Either way, it’s up to the user to not have two writers to the same path.)
+	fh, err := os.OpenFile(ref.path, os.O_WRONLY|os.O_CREATE, 0644)
 	if err != nil {
-		// FIXME: It should be possible to modify archives, but the only really
-		//        sane way of doing it is to create a copy of the image, modify
-		//        it and then do a rename(2).
-		if os.IsExist(err) {
-			err = errors.New("docker-archive doesn't support modifying existing images")
-		}
-		return nil, err
+		return nil, errors.Wrapf(err, "error opening file %q", ref.path)
+	}
+
+	fhStat, err := fh.Stat()
+	if err != nil {
+		return nil, errors.Wrapf(err, "error statting file %q", ref.path)
+	}
+
+	if fhStat.Mode().IsRegular() && fhStat.Size() != 0 {
+		return nil, errors.New("docker-archive doesn't support modifying existing images")
 	}
 
 	return &archiveImageDestination{