nat: Close the connection after we couldn't find the user

In case the token was not correct, just close the connection.
It is not clear that forcing a new TCP connection is going to
give us any extra security here. But with the upcoming auth
handling it does make sense to have both case look similar.

openbsc/src/osmo-bsc_nat/bsc_nat.c

@@ -985,6 +985,7 @@ static void ipaccess_auth_bsc(struct tlv_parsed *tvp, struct bsc_connection *bsc
 		LOGP(DNAT, LOGL_ERROR,
 			"No bsc found for token '%s' on fd: %d.\n", token,
 			bsc->write_queue.bfd.fd);
+		bsc_close_connection(bsc);
 		return;
 	}