testing: Migrate MOBIKE tests to vici

Note that the mobike-nat test has been removed as it basically did the same
as the mobike-virtual-ip-nat test.  Instead, the mobike-nat-mapping scenario
is added, which simulates a NAT router restart.

testing/tests/ikev2/mobike-nat-mappings/posttest.dat

@@ -0,0 +1,5 @@
+alice::systemctl stop strongswan
+sun::systemctl stop strongswan
+alice::iptables-restore < /etc/iptables.flush
+sun::iptables-restore < /etc/iptables.flush
+moon::iptables -t nat -F