netfilter: conntrack: fix error path in nf_conntrack_pernet_init()

When nf_ct_netns_get() fails, it should clean up itself,
its caller doesn't need to call nf_conntrack_fini_net().

nf_conntrack_init_net() is called after registering sysctl
and proc, so its cleanup function should be called before
unregistering sysctl and proc.

Fixes: ba3fbe66 ("netfilter: nf_conntrack: provide modparam to always register conntrack hooks")
Fixes: b884fa46 ("netfilter: conntrack: unify sysctl handling")
Reported-and-tested-by: syzbot+fcee88b2d87f0539dfe9@syzkaller.appspotmail.com
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_standalone.c

@@ -1115,11 +1115,11 @@ static int nf_conntrack_pernet_init(struct net *net)
 	return 0;
 
 out_hooks:
-	nf_conntrack_fini_net(net);
+	nf_conntrack_cleanup_net(net);
 out_init_net:
 	nf_conntrack_standalone_fini_proc(net);
 out_proc:
-	nf_conntrack_cleanup_net(net);
+	nf_conntrack_standalone_fini_sysctl(net);
 	return ret;
 }