iptable: fix tests timeouts

Tests were run assuming a runtime of "runsc" was present, and did not
have --net-raw enabled.

scripts/iptables_tests.sh

@@ -16,7 +16,7 @@
 
 source $(dirname $0)/common.sh
 
-install_runsc_for_test iptables
+install_runsc_for_test iptables --net-raw
 
 # Build the docker image for the test.
 run //test/iptables/runner:runner-image --norun
@@ -26,5 +26,5 @@ test //test/iptables:iptables_test \
   "--test_arg=--image=bazel/test/iptables/runner:runner-image"
 
 test //test/iptables:iptables_test \
-  "--test_arg=--runtime=runsc" \
+  "--test_arg=--runtime=${RUNTIME}" \
   "--test_arg=--image=bazel/test/iptables/runner:runner-image"