testing: Avoid delays with ping by using -W and -i options

With -W we reduce timeouts when we don't expect a response.  With -i the
interval between pings is reduced (mostly in case of auto=route where
the first ping yields no reply).

testing/tests/pfkey/net2net-route/pretest.dat

@@ -3,4 +3,4 @@ sun::iptables-restore < /etc/iptables.rules
 moon::ipsec start
 sun::ipsec start
 moon::expect-connection net-net
-alice::ping -c 10 PH_IP_BOB
+alice::ping -c 3 -W 1 -i 0.2 PH_IP_BOB