net: give better error messages

Add address and/or port to errors where applicable for better reporting.

See #7005
Actually, why don't you do this operation to `additions` before running `_extend(e, additions)`. Guess it would look like so:
```javascript
if (additions && isObject(additions)) {
  var keys = Object.keys(additions);
  for (var i = 0; i < keys.length; i++) {
    if (isNullOrUndefined(keys[i] || isFunction(keys[i])) {
      delete additions[keys[i]];
      keys.splice(i, 1);
      i--;
    }
  }
  exports._extend(e, additions);
}
```