selftests: netfilter: Pass family parameter "-f" to conntrack tool

Fix nft_conntrack_helper.sh false fail report:

1) Conntrack tool need "-f ipv6" parameter to show out ipv6 traffic items.

2) Sleep 1 second after background nc send packet, to make sure check
is after this statement executed.

False report:
FAIL: ns1-lkjUemYw did not show attached helper ip set via ruleset
PASS: ns1-lkjUemYw connection on port 2121 has ftp helper attached
...

After fix:
PASS: ns1-2hUniwU2 connection on port 2121 has ftp helper attached
PASS: ns2-2hUniwU2 connection on port 2121 has ftp helper attached
...

Fixes: 619ae8e0697a6 ("selftests: netfilter: add test case for conntrack helper assignment")
Signed-off-by: Chen Yi <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

tools/testing/selftests/netfilter/nft_conntrack_helper.sh

···
 	local message=$2
 	local port=$3
 
-	ip netns exec ${netns} conntrack -L -p tcp --dport $port 2> /dev/null |grep -q 'helper=ftp'
+	if echo $message |grep -q 'ipv6';then
+		local family="ipv6"
+	else
+		local family="ipv4"
+	fi
+
+	ip netns exec ${netns} conntrack -L -f $family -p tcp --dport $port 2> /dev/null |grep -q 'helper=ftp'
 	if [ $? -ne 0 ] ; then
 		echo "FAIL: ${netns} did not show attached helper $message" 1>&2
 		ret=1
···
 
 	sleep 3 | ip netns exec ${ns2} nc -w 2 -l -p $port > /dev/null &
 
-	sleep 1
 	sleep 1 | ip netns exec ${ns1} nc -w 2 10.0.1.2 $port > /dev/null &
+	sleep 1
 
 	check_for_helper "$ns1" "ip $msg" $port
 	check_for_helper "$ns2" "ip $msg" $port
···
 
 	sleep 3 | ip netns exec ${ns2} nc -w 2 -6 -l -p $port > /dev/null &
 
-	sleep 1
 	sleep 1 | ip netns exec ${ns1} nc -w 2 -6 dead:1::2 $port > /dev/null &
+	sleep 1
 
 	check_for_helper "$ns1" "ipv6 $msg" $port
 	check_for_helper "$ns2" "ipv6 $msg" $port