Fix resultCodes from WifiPickerActivity

This fixes the Wifi Activity inside SetupWizard.

The android.net.wifi.PICK_WIFI_NETWORK intent is received by
WifiPickerActivity, and then WifiPickerActivity launches the
WifiSettings Fragment, and then WifiSettings launches WifiSettings2, and
then WifiSettings finishes itself. (This is assuming that the
SETTINGS_WIFITRACKER2 feature flag is enabled.)

Instead of relying on WifiSettings to launch WifiSettings2, we should
just launch WifiSettings2 directly. If we don't do this, WifiSettings
finishing itself will send a resultCode of RESULT_CANCELLED to the app
that launched an Intent with action android.net.wifi.PICK_WIFI_NETWORK.
This means that the resultCode from WifiSettings2 will never get
propagated.

Change-Id: Ia4171b72d6213f902a820163ecaf1fb4eae4e6e6