netfilter: nf_tables: unbind non-anonymous set if rule construction fails

commit 3e704897 upstream.

Otherwise a dangling reference to a rule object that is gone remains
in the set binding list.

Fixes: 26b5a571

 ("netfilter: nf_tables: add NFT_TRANS_PREPARE_ERROR to deal with bound set/chain")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>