MINOR: quic: Release asap quic_conn memory (application level)

Add a check to the QUIC packet handler running at application level (after the
handshake is complete) to release the quic_conn memory calling quic_conn_release().
This is done only if the mux is not started.

src/quic_conn.c

@@ -743,6 +743,11 @@ struct task *quic_conn_app_io_cb(struct task *t, void *context, unsigned int sta
 	}
 
  out:
+	if ((qc->flags & QUIC_FL_CONN_CLOSING) && qc->mux_state != QC_MUX_READY) {
+		quic_conn_release(qc);
+		qc = NULL;
+	}
+
 	TRACE_LEAVE(QUIC_EV_CONN_IO_CB, qc);
 	return t;
 }