QUIC: fixed triggering stream read event (ticket #2409).

QUIC: fixed triggering stream read event (ticket #2409).

If a client packet carrying a stream data frame is not acked due to packet loss,
the stream data is retransmitted later by client.  It's also possible that the
retransmitted range is bigger than before due to more stream data being
available by then.  If the original data was read out by the application,
there would be no read event triggered by the retransmitted frame, even though
it contains new data.