overlay: do not clone source recursively

do not clone the source directory in recursive mode (the equivalent of
MS_BIND|MS_RECURSIVE) but use only a regular bind mount.  If
not recursive bind mount is used then the existing overlay mounts are
not replicated.  In this way a new idmapped mount won't need to map
the overlay mount as well, causing the mount_settattr(2) syscall to
fail with EINVAL since it is not possible to idmap an overlay mount
yet.

Closes: containers#1308

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

drivers/overlay/idmapped_utils.go

@@ -105,7 +105,7 @@ func createIDMappedMount(source, target string, pid int) error {
 
 	defer userNsFile.Close()
 
-	targetDirFd, err := openTree(source, _OPEN_TREE_CLONE|unix.AT_RECURSIVE)
+	targetDirFd, err := openTree(source, _OPEN_TREE_CLONE)
 	if err != nil {
 		return err
 	}