Emit Disconnect event properly on connection reset without handshake

[Rakowskiii]

The websocket relay client will currently only emit Error event when the connection is finished not gracefully. It should also emit Disconnected otherwise consumer may think the connection is intact, while in fact it's dead.

This is what happens currently (e.g. when relay is redeployed)

[cast-client] inbound error: Websocket client error: Websocket transport error: WebSocket protocol error: Connection reset without closing handshake