Skip aufs whiteout files on userns translation to container

aufs kernel module creates whiteout files on upper layer delete (and
other situations) and those files already are 'translated' regarding
ownership in host terms (e.g. they are already "0:0" owned), so when
these layers are copied around with pkg/archive we don't want to try and
translate these files regarding ownership.

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)

pkg/archive/archive.go

@@ -304,8 +304,9 @@ func (ta *tarAppender) addTarFile(path, name string) error {
 	}
 
 	//handle re-mapping container ID mappings back to host ID mappings before
-	//writing tar headers/files
-	if ta.UIDMaps != nil || ta.GIDMaps != nil {
+	//writing tar headers/files. We skip whiteout files because they were written
+	//by the kernel and already have proper ownership relative to the host
+	if !strings.HasPrefix(filepath.Base(hdr.Name), WhiteoutPrefix) && (ta.UIDMaps != nil || ta.GIDMaps != nil) {
 		uid, gid, err := getFileUIDGID(fi.Sys())
 		if err != nil {
 			return err