Disable IPv4 forwarding on carol in order to pass tnc/tnccs-20-os scenario

testing/tests/tnc/tnccs-20-os/posttest.dat

@@ -4,3 +4,4 @@ dave::ipsec stop
 moon::/etc/init.d/iptables stop 2> /dev/null
 carol::/etc/init.d/iptables stop 2> /dev/null
 dave::/etc/init.d/iptables stop 2> /dev/null
+carol::echo 1 > /proc/sys/net/ipv4/ip_forward

testing/tests/tnc/tnccs-20-os/pretest.dat

@@ -1,6 +1,7 @@
 moon::/etc/init.d/iptables start 2> /dev/null
 carol::/etc/init.d/iptables start 2> /dev/null
 dave::/etc/init.d/iptables start 2> /dev/null
+carol::echo 0 > /proc/sys/net/ipv4/ip_forward
 moon::cat /etc/tnc_config
 carol::cat /etc/tnc_config
 dave::cat /etc/tnc_config