dbus: Add virtual interface create/remove logic to be inline with ctrl_iface

dbus: Add virtual interface create/remove logic to be inline with ctrl_iface

There is no way to create or remove a virtual interface with
wpa_supplicant dbus methods. The platform has to use out-of-band methods
to manage the virtual interfaces.

This change adds virtual interface create/remove logic to the dbus
methods CreateInterface and RemoveInterface to achieve similar
functionalities as wpa_cli commands interface_add and interface_remove.

Signed-off-by: Jintao Lin <jintaolin@chromium.org>