Pyface filedialog does not use native file dialog and (thus) cannot see remote path (UNC path)

I tested PyQt4 QFileDialog, it uses the native FileDialog in both macOS and Windows 10 .
Below is how I test PyQt4 FileDialog:

```
from PyQt4 import QtGui
import sys

QtGui.QApplication(sys.argv)
QtGui.QFileDialog.getOpenFileName()
sys.exit(app.exec_())
```

Below is how I use pyface FileDialog:

```
from pyface.api import FileDialog, OK
dlg = FileDialog(action='open')
if dlg.open() == OK:
pass
```