Allow driver and ctrl_interface parameters to be overridden

Allow driver and ctrl_interface parameters to be overridden

New wpa_supplicant command line options -o<driver> and -O<ctrl> can
now be used to override the parameters received in add interface
command from dbus or global ctrl_interface. This can be used, e.g.,
to enable control interface when using NetworkManager (add
-O/var/run/wpa_supplicant into the Exec parameter in
/usr/share/dbus-1/system-services/fi.epitest.hostap.WPASupplicant.service).
Similarly, this can be used to use another driver wrapper with
NetworkManager (e.g., -onl80211 to replace WEXT with nl80211).