selftests: net: using ping6 for IPv6 in udpgro_fwd.sh

udpgro_fwd.sh output following message:
  ping: 2001:db8:1:💯 Address family for hostname not supported

Using ping6 when pinging IPv6 addresses.

Fixes: a062260a9d ("selftests: net: add UDP GRO forwarding self-tests")
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/udpgro_fwd.sh

@@ -185,6 +185,7 @@ for family in 4 6; do
 	IPT=iptables
 	SUFFIX=24
 	VXDEV=vxlan
+	PING=ping
 
 	if [ $family = 6 ]; then
 		BM_NET=$BM_NET_V6
@@ -192,6 +193,7 @@ for family in 4 6; do
 		SUFFIX="64 nodad"
 		VXDEV=vxlan6
 		IPT=ip6tables
+		PING="ping6"
 	fi
 
 	echo "IPv$family"
@@ -237,7 +239,7 @@ for family in 4 6; do
 
 	# load arp cache before running the test to reduce the amount of
 	# stray traffic on top of the UDP tunnel
-	ip netns exec $NS_SRC ping -q -c 1 $OL_NET$DST_NAT >/dev/null
+	ip netns exec $NS_SRC $PING -q -c 1 $OL_NET$DST_NAT >/dev/null
 	run_test "GRO fwd over UDP tunnel" $OL_NET$DST_NAT 1 1 $OL_NET$DST
 	cleanup