Fix handling of waiting for drain event

[kastermester]

When sendToQueue returns false what is indicated is that it was not possible to write to the network stream right now - and instead the buffer is stored in user space memory for when the socket is ready again.

The current logic takes this to mean "the message could not be sent, wait for drain and try agian after this". This means that effectively we can end up sending the message twice when it is not needed.

[kastermester]

See: https://nodejs.org/docs/latest-v14.x/api/net.html#net_socket_write_data_encoding_callback

Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory. 'drain' will be emitted when the buffer is again free.