Refine the check restriction function in WifiEntryPreference

- Move checkRestrictionAndSetDisabled function from WifiEntryPreference to necessary child-classes to avoid impacting other child-classes such as SavedAccessPointsPreference.

- Avoid adding ShadowRestrictedPreference to the unnecessary test class.

Bug: 233871529
Test: manual test
make RunSettingsRoboTests

Change-Id: Ia2145401558b293b5f4eaa0860f83b7d3bbab548

src/com/android/settings/wifi/WifiEntryPreference.java

@@ -21,7 +21,6 @@ import android.content.res.Resources;
 import android.content.res.TypedArray;
 import android.graphics.drawable.Drawable;
 import android.graphics.drawable.StateListDrawable;
-import android.os.UserManager;
 import android.text.TextUtils;
 import android.view.View;
 import android.widget.ImageButton;
@@ -88,7 +87,6 @@ public class WifiEntryPreference extends RestrictedPreference implements
         mWifiEntry = wifiEntry;
         mWifiEntry.setListener(this);
         mIconInjector = iconInjector;
-        checkRestrictionAndSetDisabled(UserManager.DISALLOW_ADD_WIFI_CONFIG);
         refresh();
     }