Sudden disconnected server is reported as ConnectionIsTimeout

[edsko]

If I have a client and a server, and I CTRL-C the server while the client is still waiting for a reply, I see a ConnectionIsTimeout on the client side, which is confusing and may lead folks down the wrong path when debugging issues. I suspect that this is due to unfortunate interaction between the timeout manager and the rest of http2, similar to #136 perhaps.