Remove existing list when force update network

Otherwise it could including previous scan result when re-enter the
page.

Fix: 336244021
Test: manual test - on NetworkSelectSettings
Change-Id: I34b4820b116868b98649202c424d2168746232e8

src/com/android/settings/network/telephony/NetworkSelectSettings.java

@@ -490,6 +490,7 @@ public class NetworkSelectSettings extends DashboardFragment {
      */
     private void forceUpdateConnectedPreferenceCategory(
             NetworkSelectRepository.NetworkRegistrationAndForbiddenInfo info) {
+        mPreferenceCategory.removeAll();
         for (NetworkRegistrationInfo regInfo : info.getNetworkList()) {
             final CellIdentity cellIdentity = regInfo.getCellIdentity();
             if (cellIdentity == null) {