Supporting ssh multiplexing

In my local `~/.ssh/config`:

```
Host *
    ControlMaster auto
    ControlPath /tmp/ssh-%r@%h:%p.socket
    ControlPersist yes
    ServerAliveCountMax 2
    ServerAliveInterval 120
```

I enabled ssh multiplexing for any connection, but `rtop` seems not to be using the `ControlPath`.

Is it possible for `rtop` to use the `ControlPath` opened by `ssh`?