netfilter: nf_tables: validate all pending tables

We have to validate all tables in the transaction that are in
VALIDATE_DO state, the blamed commit below did not move the break
statement to its right location so we only validate one table.

Moreover, we can't init table->validate to _SKIP when a table object
is allocated.

If we do, then if a transcaction creates a new table and then
fails the transaction, nfnetlink will loop and nft will hang until
user cancels the command.

Add back the pernet state as a place to stash the last state encountered.
This is either _DO (we hit an error during commit validation) or _SKIP
(transaction passed all checks).

Fixes: 00c320f9 ("netfilter: nf_tables: make validation state per table")
Reported-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>