Fix settings page flicker in two ways:

1. On create use UiBlocker as recommended by settings team
2. On resume only update the preferences list if the system setting has
   changed.

Bug: 220837804
Test: manual
Change-Id: Ieebd2e7fd74ab05d4fb73aede6868553d7d84af1

tests/robotests/src/com/android/settings/location/LocationSettingsTest.java

@@ -20,6 +20,7 @@ import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import android.content.ContentResolver;
 import android.content.Context;
 import android.os.Bundle;
 
@@ -41,6 +42,8 @@ public class LocationSettingsTest {
     private SettingsActivity mActivity;
     @Mock
     private SettingsMainSwitchBar mSwitchBar;
+    @Mock
+    private ContentResolver mContentResolver;
 
     private Context mContext;
     private LocationSettings mLocationSettings;
@@ -52,6 +55,7 @@ public class LocationSettingsTest {
         mLocationSettings = spy(new LocationSettings());
         doReturn(mActivity).when(mLocationSettings).getActivity();
         doReturn(mContext).when(mLocationSettings).getContext();
+        doReturn(mContentResolver).when(mActivity).getContentResolver();
         when(mActivity.getSwitchBar()).thenReturn(mSwitchBar);
     }