Bug:PreferredNetworkModePreferenceController.java not being refreshed

Bug: 146594872
Test: make RunSettingsRoboTests ROBOTEST_FILTER=\
PreferredNetworkModePreferenceControllerTest (PASS)

Change-Id: Ib5cc06cdbfd2fa70cd115d70337b21500e362da6

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

@@ -85,6 +85,8 @@ public class PreferredNetworkModePreferenceController extends TelephonyBasePrefe
             Settings.Global.putInt(mContext.getContentResolver(),
                     Settings.Global.PREFERRED_NETWORK_MODE + mSubId,
                     newPreferredNetworkMode);
+            final ListPreference listPreference = (ListPreference) preference;
+            listPreference.setSummary(getPreferredNetworkModeSummaryResId(newPreferredNetworkMode));
             return true;
         }