Fixes back button on action bar on some fragments.

SettingsPreferenceFragment has this already set so that the drawer
layout will work when the menu doesn't exist. However, some fragments
are not preference fragments, and we need to set setHasOptionsMenu
manually.

bug:27879503
Change-Id: I6faadeb56dab00af611ac413109800822038c66d

src/com/android/settings/DeviceAdminSettings.java

@@ -119,7 +119,7 @@ public class DeviceAdminSettings extends ListFragment {
     @Override
     public void onActivityCreated(Bundle savedInstanceState) {
         super.onActivityCreated(savedInstanceState);
-
+        setHasOptionsMenu(true);
         Utils.forceCustomPadding(getListView(), true /* additive padding */);
     }