ikev2: close an established IKE_SA when receiving AUTHENTICATION_FAILED

RFC 5996 compatible implementations MAY send an INFORMATIONAL message
with an AUTHENTICATION_FAILED if the initiator failed to authenticate us.
Handle such a message like a DELETE for an IKE_SA.

src/libcharon/sa/ikev2/task_manager_v2.c

@@ -849,6 +849,12 @@ static status_t process_request(private_task_manager_t *this,
 									task = (task_t*)ike_auth_lifetime_create(
 															this->ike_sa, FALSE);
 									break;
+								case AUTHENTICATION_FAILED:
+									/* initiator failed to authenticate us.
+									 * We use ike_delete to handle this, which
+									 * invokes all the required hooks. */
+									task = (task_t*)ike_delete_create(
+														this->ike_sa, FALSE);
 								default:
 									break;
 							}