netfilter: nf_tables: fix wrong destroy anonymous sets if binding fails

When we add a nft rule like follows:
  # nft add rule filter test tcp dport vmap {1: jump test}
-ELOOP error will be returned, and the anonymous set will be
destroyed.

But after that, nf_tables_abort will also try to remove the
element and destroy the set, which was already destroyed and
freed.

If we add a nft wrong rule, nft_tables_abort will do the cleanup
work rightly, so nf_tables_set_destroy call here is redundant and
wrong, remove it.

Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>