libnftables: Keep cmds list outside of parser_state

libnftables: Keep cmds list outside of parser_state

Parser basically turns input into a list of commands and error messages.
Having the commands list being part of struct parser_state does not make
sense from this point of view, also it will have to go away with
upcoming JSON support anyway.

While being at it, change nft_netlink() to take just the list of
commands instead of the whole parser state as parameter, also take care
of command freeing in nft_run_cmd_from_* functions (where the list
resides as auto-variable) instead of from inside nft_run().

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>