Basic pluto with IKEv2 using PSK on the initiator (west), and Strongswan on
the responder.

This uses  ike and esp values of aes128-sha1 on both sides.

Note: libreswan uses the "aes" shortcut to mean "aes256", while
strongswan uses the "aes" shortcut to mean "aes256". This means
specifying ike=aes-sha1 on both sides will fail to work.


