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