Settings: Use public API for mac randomization support

Also, don't directly reference the default tether ssid overlay. This info
should always be retrieved from wifiManager.
This ensures that we don't use wifi overlays in settings.

Bug: 143464763
Test: atest com.android.server.wifi
Change-Id: I893a4ca0f4243e1eb6f9c8bef810d0b4a493fb88

src/com/android/settings/homepage/contextualcards/conditional/HotspotConditionController.java

@@ -116,8 +116,8 @@ public class HotspotConditionController implements ConditionalCardController {
     private CharSequence getSsid() {
         WifiConfiguration wifiConfig = mWifiManager.getWifiApConfiguration();
         if (wifiConfig == null) {
-            return mAppContext.getText(
-                    com.android.internal.R.string.wifi_tether_configure_ssid_default);
+            // Should never happen.
+            return "";
         } else {
             return wifiConfig.SSID;
         }