netfilter: nf_tables: fix nft_counters_enabled underflow at nf_tables_addchain()

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_tables: fix nft_counters_enabled underflow at nf_tables_addchain()

syzbot is reporting underflow of nft_counters_enabled counter at

nf_tables_addchain() [1], for commit 43eb8949cfdffa76 ("netfilter:

nf_tables: do not leave chain stats enabled on error") missed that

nf_tables_chain_destroy() after nft_basechain_init() in the error path of

nf_tables_addchain() decrements the counter because nft_basechain_init()

makes nft_is_base_chain() return true by setting NFT_CHAIN_BASE flag.

Increment the counter immediately after returning from

nft_basechain_init().