In some cases (especially if a child is half-open) the colliding
rekey-job might not have created the ike_init member. If so, the
nonce check fails with SIGSEGV.
This output helps tracing checkout and checkin of IKE_SAs when there is
more than one IKE_SAs with the same name. I also added the type of
in-air-exchange to the debug output issued by the task_manager in case
a task initiation is delayed, came in handy for me.