Fix logging spam in DashboardFragment.

When updating preferences managed through PreferenceController, the
fragment should skip prefs that are not available.

Bug: 32255863
Test: RunSettingsRoboTests
Change-Id: I2f9b6ddf8c78d40068dc18f07e60672dcba4474a

src/com/android/settings/deviceinfo/AdditionalSystemUpdatePreferenceController.java

@@ -34,7 +34,7 @@ public class AdditionalSystemUpdatePreferenceController extends PreferenceContro
     }
 
     @Override
-    protected boolean isAvailable() {
+    public boolean isAvailable() {
         return mContext.getResources().getBoolean(
                 com.android.settings.R.bool.config_additional_system_update_setting_enable);
     }

src/com/android/settings/deviceinfo/ManageStoragePreferenceController.java

@@ -17,13 +17,10 @@ package com.android.settings.deviceinfo;
 
 import android.content.Context;
 import android.support.v7.preference.Preference;
-import android.support.v7.preference.PreferenceScreen;
 
 import com.android.settings.R;
 import com.android.settings.core.PreferenceController;
 
-import java.util.List;
-
 public class ManageStoragePreferenceController extends PreferenceController {
 
     public static final String KEY_MANAGE_STORAGE = "pref_manage_storage";
@@ -43,7 +40,7 @@ public class ManageStoragePreferenceController extends PreferenceController {
     }
 
     @Override
-    protected boolean isAvailable() {
+    public boolean isAvailable() {
         return mContext.getResources().getBoolean(R.bool.config_storage_manager_settings_enabled);
     }
 }

src/com/android/settings/deviceinfo/SystemUpdatePreferenceController.java

@@ -46,7 +46,7 @@ public class SystemUpdatePreferenceController extends PreferenceController {
     }
 
     @Override
-    protected boolean isAvailable() {
+    public boolean isAvailable() {
         return mUm.isAdminUser();
     }