Properly forget networks and refresh page in SavedAcessPointsWifiSettings.

The dialog access point rebuilt after fragment is destroyed (i.e.
orientation change) did not properly save selected Preference, and
caused NPE. Changed onForget to refresh preference list.

Bug: 35207121
Test: b/35322875 tracking bug for saved networks tests.
Change-Id: I81935c5a6e3efab4d4e3b6e7c2b150bacf06d7c1