isCarrierNetworkActive() should check if the carrier network is default

WifiPickerTrackerHelper should use MergedCarrierEntry.isDefaultNetwork()
for isCarrierNetworkActive().

Bug: 191090765
Test: atest WifiPickerTrackerHelperTest
Change-Id: I44d8eed3af019a8d6a30a4b743cad468d1f0469b

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

@@ -142,11 +142,7 @@ public class WifiPickerTrackerHelper implements LifecycleObserver {
     /** Confirms connection of the carrier network connected with the internet access */
     public boolean isCarrierNetworkActive() {
         final MergedCarrierEntry mergedCarrierEntry = mWifiPickerTracker.getMergedCarrierEntry();
-        if (mergedCarrierEntry != null) {
-            return mergedCarrierEntry.getConnectedState() == WifiEntry.CONNECTED_STATE_CONNECTED
-                    && mergedCarrierEntry.hasInternetAccess();
-        }
-        return false;
+        return (mergedCarrierEntry != null && mergedCarrierEntry.isDefaultNetwork());
     }
 
     /** Return the carrier network ssid */