charon-tkm: Call esa_reset() when the inbound SA is deleted

charon-tkm: Call esa_reset() when the inbound SA is deleted

After a rekeying the outbound SA and policy is deleted immediately, however,
the inbound SA is not removed until a few seconds later, so delayed packets
can still be processed.

This adds a flag to get_esa_id() that specifies the location of the
given SPI.