fix flaky tests

[marten-seemann]

Depends on #119.

The problem here was that the test stream handler would write the autonat response right away, and then close the stream (which send a FIN for the write side and resets the read side of the stream).
This would then trip up the peer when it tries to write the message:

go-libp2p-autonat/client.go

Lines 46 to 50 in 12fc177

	req := newDialMessage(peer.AddrInfo{ID: c.h.ID(), Addrs: c.addrFunc()})
	if err := w.WriteMsg(req); err != nil {
	s.Reset()
	return nil, err
	}

The fix is easy: read the client's message first, only then send the response.

[marten-seemann]

Just that this fix apparently doesn't work. Debugging...

[marten-seemann]

The reason for the failure was: #119 (comment).