Don't load anything from contextual card db in legacy mode.

Change-Id: I2fa1ee78bb8878c2cf46fd2f59499c9ed8eb0a09
Fixes: 124246284
Test: robotest

tests/robotests/src/com/android/settings/homepage/contextualcards/ContextualCardLoaderTest.java

@@ -27,6 +27,7 @@ import static org.mockito.Mockito.spy;
 import android.content.Context;
 import android.net.Uri;
 
+import com.android.settings.R;
 import com.android.settings.slices.CustomSliceRegistry;
 
 import org.junit.Before;
@@ -132,6 +133,14 @@ public class ContextualCardLoaderTest {
         assertThat(result).hasSize(2);
     }
 
+    @Test
+    public void loadInBackground_legacyMode_shouldReturnNothing() {
+        assertThat(mContext.getResources().getBoolean(R.bool.config_use_legacy_suggestion))
+                .isTrue();
+
+        assertThat(mContextualCardLoader.loadInBackground()).isEmpty();
+    }
+
     private ContextualCard getContextualCard(String sliceUri) {
         return new ContextualCard.Builder()
                 .setName("test_card")