testing: Make per-CPU SAs scenarios more predictable by pinning IRQs to vCPUs

This ensures that packets on sun are processed on a particular CPU and
not randomly on one, which causes expected SAs not to get created or
other weird things.

testing/tests/ikev2/per-cpu-sas/posttest.dat

@@ -3,3 +3,4 @@ moon::systemctl stop strongswan
 sun::systemctl stop strongswan
 moon::iptables-restore < /etc/iptables.flush
 sun::iptables-restore < /etc/iptables.flush
+sun::set-cpu-affinity eth1 0-1

testing/tests/ikev2/per-cpu-sas/pretest.dat

@@ -1,3 +1,5 @@
+# make sure forwarded responses trigger IRQ on the right CPU
+sun::set-cpu-affinity eth1 0
 sun::iptables-restore < /etc/iptables.rules
 moon::iptables-restore < /etc/iptables.rules
 sun::systemctl start strongswan