reconnect: fix callback when not currently connected
The 'disconnected' event is normally fired from connection_lost(), which is called by the connection code when the connection is lost after being established. However, if the connection wasn't successfully established, a manual /reconnect no-ops because it waits for the 'disconnected' callback which never fires. This patch does two things: 1. Immediately fire a 'disconnected' event in disconnect() if there is no transport. 2. Register the 'disconnected' event handler in reconnect() *before* it can be fired.