nft-compat: create a separated object update type to rename chains

This patch adds an explicit object update type to rename chains, so we avoid
calling the nf_tables API with NLM_F_EXCL.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>