Active timeout on QUIC

[maskit]

Active timeout is not handled on QUIC connection. On the test box for interop, I saw a client that keep sending PING for hours.

#5824

[scw00]

It seems spec doesn't say what we should do when active timeout happen. It should be handled by application rather than a connection.

[maskit]

Well, I guess TCP neither. Also PING is a part of transport.