Current codes invoke wrongly nf_ct_netns_get in the destroy routine,
it should use nf_ct_netns_put, not nf_ct_netns_get.
It could cause some modules could not be unloaded.
Fixes: ecb2421b5ddf ("netfilter: add and use nf_ct_netns_get/put") Signed-off-by: Gao Feng <fgao@ikuai8.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>