tls-eap: Conclude EAP method also after processing packets

With TLS 1.3, the server sends its Finished message first, so the
session is complete after processing the client's Finished message,
without having to send anything else (in particular no acknowledgement
as the last message from the client is no fragment).

src/libtls/tls_eap.c

@@ -394,6 +394,10 @@ METHOD(tls_eap_t, process, status_t,
 	switch (status)
 	{
 		case INVALID_STATE:
+			if (this->tls->is_complete(this->tls))
+			{
+				return SUCCESS;
+			}
 			*out = create_ack(this);
 			return NEED_MORE;
 		case FAILED: