Allow user configuration of IKE retransmission
When using IKEv2,
dpd_timeout is ignored and instead the global
charon.retransmit_* is used to determine the timeout thresholds of the IKE connection. As is, the timeout can last for several minutes.
The retransmission options should be user-configurable. This would help, for example, in HA failover scenarios where a low retransmission timeout could result in a significantly quicker IPsec reconnection.