Interop with strongswan, original IKE initiator, west, rekeying IPsec SA.

West, libreswan, is the original IKE initiator.
West, strongswan, is the original IKE responder. West will rekey the IKE SA using
CREATE_CHILD_SA exchange  RFC 7296 #1.3.2
The libreswan, east, is the original initiator and the responder to Child rekey.
