Fix for Codeception issue #1510 - site-root relative paths

Using a site-root relative path for a form's action fails if PhpBrowser
is configured with a 'url' basepath with a subdir (e.g.
localhost/subdir)
I don't see any reasons why can't you build url with just concatenating url parts

```
$url = isset($parts['scheme']) ? $parts['scheme'] . '://' : '';
$url .= $parts['host'];
if (isset($parts['port'])) { $url .= ':'$parts['port']);
```

at least this is much readable and can be easily narrowed down on debugging