c8d/mount: Create same directory owners as graphdrivers

Graph drivers create the parent directory with
rootPair().GID:CurrentIdentity().UID owner. This change brings these in
line

Signed-off-by: Djordje Lukic <djordje.lukic@docker.com>

daemon/snapshotter/mount.go

@@ -93,7 +93,13 @@ func (m *refCountMounter) Mount(mounts []mount.Mount, containerID string) (targe
 	}()
 
 	root := m.idMap.RootPair()
-	if err := idtools.MkdirAllAndChown(target, 0o700, root); err != nil {
+	if err := idtools.MkdirAllAndChown(filepath.Dir(target), 0o710, idtools.Identity{
+		UID: idtools.CurrentIdentity().UID,
+		GID: root.GID,
+	}); err != nil {
+		return "", err
+	}
+	if err := idtools.MkdirAllAndChown(target, 0o710, root); err != nil {
 		return "", err
 	}