selftests/net: packetdrill: increase timing tolerance in debug mode

Some packetdrill tests are flaky in debug mode. As discussed, increase
tolerance.

We have been doing this for debug builds outside ksft too.

Previous setting was 10000. A manual 50 runs in virtme-ng showed two
failures that needed 12000. To be on the safe side, Increase to 14000.

Link: https://lore.kernel.org/netdev/Zuhhe4-MQHd3EkfN@mini-arch/
Fixes: 1e42f73fd3c2 ("selftests/net: packetdrill: import tcp/zerocopy")
Reported-by: Stanislav Fomichev <[e-mail]>
Signed-off-by: Willem de Bruijn <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Acked-by: Stanislav Fomichev <[e-mail]>
Acked-by: Matthieu Baerts (NGI0) <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

tools/testing/selftests/net/packetdrill/ksft_runner.sh

···
 	exit "$KSFT_SKIP"
 fi
 
+declare -a optargs
+if [[ -n "${KSFT_MACHINE_SLOW}" ]]; then
+	optargs+=('--tolerance_usecs=14000')
+fi
+
 ktap_print_header
 ktap_set_plan 2
 
-unshare -n packetdrill ${ipv4_args[@]} $(basename $script) > /dev/null \
+unshare -n packetdrill ${ipv4_args[@]} ${optargs[@]} $(basename $script) > /dev/null \
 	&& ktap_test_pass "ipv4" || ktap_test_fail "ipv4"
-unshare -n packetdrill ${ipv6_args[@]} $(basename $script) > /dev/null \
+unshare -n packetdrill ${ipv6_args[@]} ${optargs[@]} $(basename $script) > /dev/null \
 	&& ktap_test_pass "ipv6" || ktap_test_fail "ipv6"
 
 ktap_finished