SSH2: make it so negotiated algorithms can be seen before login

Okay. Thanks for the explanation.

I wasn't necessarily talking about removing the early return. In particular, it looks like you could replace 
```
if (!($this->bitmap & NET_SSH2_MASK_CONSTRUCTOR)) {
    if (!$this->_connect()) {
        return false;
    }
}
```

```
if (!$this->_connect()) {
    return false;
}
```