libipsec: Insert SAs first, so latest SA with the same reqid gets used

This was useful for testing purposes of RADIUS accounting, but OS kernels
generally will use the latest SA, so we do the same.

src/libipsec/ipsec_sa_mgr.c

@@ -482,7 +482,7 @@ METHOD(ipsec_sa_mgr_t, add_sa, status_t,
 
 	entry = create_entry(sa_new);
 	schedule_expiration(this, entry);
-	this->sas->insert_last(this->sas, entry);
+	this->sas->insert_first(this->sas, entry);
 
 	this->mutex->unlock(this->mutex);
 	return SUCCESS;