evaluate: only allow stateful statements in set and map definitions

evaluate: only allow stateful statements in set and map definitions

The bison parser doesn't allow this to happen due to grammar
restrictions, but the json input has no such issues.

The bogon input assigns 'notrack' which triggers:
BUG: unknown stateful statement type 19
nft: src/netlink_linearize.c:1061: netlink_gen_stmt_stateful: Assertion `0' failed.

After patch, we get:
Error: map statement must be stateful

Fixes: 07958ec53830 ("json: add set statement list support")
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>