ip_set: Pass init_net when @net is missing in match check params data structure

ip_set: Pass init_net when @net is missing in match check params data structure

It is better to restrict ipsets to default network namespace on old
kernels that does not contain @net parameter in @struct xt_mtchk_param
(i.e. ones prior to commit a83d8e8d099f ("netfilter: xtables:
add struct xt_mtchk_param::net"), tag v2.6.34) instead of panicing
on them.

Found and tested on RHEL 6 with 2.6.32 kernels.

Fixes: 90e279db0cf5 ("Add more compatibility checkings to support older kernel releases")
Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>