Fix crash due to UserManager is null.

- Instance of UserManager get from onCraete, so  we can not use this
   onAttach.

Flag: EXEMPT bug fix
Fix: 289232540
Test: Manual test
Change-Id: Ieb62d8289db0dbcd5a16280aa66f3b3de8936e26

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

@@ -202,12 +202,6 @@ public class MobileNetworkSettings extends AbstractMobileNetworkSettings impleme
     @Override
     public void onAttach(Context context) {
         super.onAttach(context);
-        if (isUiRestricted()) {
-            Log.d(LOG_TAG, "Mobile network page is disallowed.");
-            finish();
-            return;
-        }
-
         if (mSubId == SubscriptionManager.INVALID_SUBSCRIPTION_ID) {
             Log.d(LOG_TAG, "Invalid subId, get the default subscription to show.");
             SubscriptionInfo info = SubscriptionUtil.getSubscriptionOrDefault(context, mSubId);
@@ -346,6 +340,11 @@ public class MobileNetworkSettings extends AbstractMobileNetworkSettings impleme
                 setTelephonyAvailabilityStatus(getPreferenceControllersAsList());
 
         super.onCreate(icicle);
+        if (isUiRestricted()) {
+            Log.d(LOG_TAG, "Mobile network page is disallowed.");
+            finish();
+            return;
+        }
         final Context context = getContext();
         mUserManager = (UserManager) context.getSystemService(Context.USER_SERVICE);
         mTelephonyManager = context.getSystemService(TelephonyManager.class)