Make write non-blocking for async transport.

src/Connection.cs

@@ -352,7 +352,7 @@ void Connect(SaslProfile saslProfile, Open open)
            if (WebSocketTransport.MatchScheme(address.Scheme))
            {
                WebSocketTransport wsTransport = new WebSocketTransport();
                wsTransport.ConnectAsync(address, null).GetAwaiter().GetResult();
                wsTransport.ConnectAsync(address, null).ConfigureAwait(false).GetAwaiter().GetResult();
                transport = wsTransport;
            }
            else

src/Net/TaskExtensions.cs

@@ -266,13 +266,24 @@ public static Task<Message> ReceiveAsync(this ReceiverLink receiver, int timeout
        internal static async Task<IAsyncTransport> OpenAsync(this SaslProfile saslProfile, string hostname,
            IBufferManager bufferManager, IAsyncTransport transport)
        {
            ProtocolHeader header = saslProfile.Start(hostname, transport);
            // if transport is closed, pump reader should throw exception
            TransportWriter writer = new TransportWriter(transport, e => { });

            ProtocolHeader myHeader = saslProfile.Start(hostname, writer);

            AsyncPump pump = new AsyncPump(bufferManager, transport);

            await pump.PumpAsync(
                h => { saslProfile.OnHeader(header, h); return true; },
                b => { SaslCode code; return saslProfile.OnFrame(transport, b, out code); });
                header =>
                {
                    saslProfile.OnHeader(myHeader, header);
                    return true;
                },
                buffer =>
                {
                    SaslCode code;
                    return saslProfile.OnFrame(writer, buffer, out code);
                });

            return (IAsyncTransport)saslProfile.UpgradeTransportInternal(transport);
        }

src/WinRT/TcpTransport.cs

@@ -83,12 +83,12 @@ public void Close()

        public void Send(ByteBuffer buffer)
        {
            this.SendAsync(new ByteBuffer[] { buffer }, buffer.Length).GetAwaiter().GetResult();
            this.SendAsync(new ByteBuffer[] { buffer }, buffer.Length).ConfigureAwait(false).GetAwaiter().GetResult();
        }

        public int Receive(byte[] buffer, int offset, int count)
        {
            return this.ReceiveAsync(buffer, offset, count).GetAwaiter().GetResult();
            return this.ReceiveAsync(buffer, offset, count).ConfigureAwait(false).GetAwaiter().GetResult();
        }
    }
}

src/WinRT/WebSocketTransport.cs

@@ -109,12 +109,12 @@ void ITransport.Close()

        void ITransport.Send(ByteBuffer buffer)
        {
            ((IAsyncTransport)this).SendAsync(new ByteBuffer[] { buffer }, buffer.Length).GetAwaiter().GetResult();
            ((IAsyncTransport)this).SendAsync(new ByteBuffer[] { buffer }, buffer.Length).ConfigureAwait(false).GetAwaiter().GetResult();
        }

        int ITransport.Receive(byte[] buffer, int offset, int count)
        {
            return ((IAsyncTransport)this).ReceiveAsync(buffer, offset, count).GetAwaiter().GetResult();
            return ((IAsyncTransport)this).ReceiveAsync(buffer, offset, count).ConfigureAwait(false).GetAwaiter().GetResult();
        }

        static int GetDefaultPort(string scheme, int port)