Play vibration preview when turning on vibration

Bug: 130332550
Test: Go to Settings > Accessibility > Vibration. Set vibration strength
to some value, then set it to off, then set it back to the previous
value. The vibration preview should be played

Change-Id: Ie28efe01fc4df5356cc0d316c1a88e518f81df41

src/com/android/settings/accessibility/VibrationPreferenceFragment.java

@@ -128,6 +128,8 @@ public abstract class VibrationPreferenceFragment extends RadioButtonPickerFragm
             // Update vibration intensity setting
             Settings.System.putInt(getContext().getContentResolver(),
                     getVibrationIntensitySetting(), candidate.getIntensity());
+        } else {
+            playVibrationPreview();
         }
     }