Fix NullPointerException in ConnectivityService

[Problem]
NullPointerException occurs in ConnectivityService when boot up.

[Root Cause]
When ConnectivityService starts up, isTetheringSupported may access
UserManager that has not been created yet. Therefore,
NullPointerException occurs.

[Solution]
Changed to create UserManager before makeTethering().

Bug: 134351774
Test: ConnectivityServiceTest
Change-Id: I299ecfa6af7295c1f3922f37d90eb5d3ab0d0286

services/core/java/com/android/server/ConnectivityService.java

@@ -966,6 +966,8 @@ public class ConnectivityService extends IConnectivityManager.Stub
             }
         }
 
+        mUserManager = (UserManager) context.getSystemService(Context.USER_SERVICE);
+
         mTethering = makeTethering();
 
         mPermissionMonitor = new PermissionMonitor(mContext, mNetd);
@@ -1013,8 +1015,6 @@ public class ConnectivityService extends IConnectivityManager.Stub
         final DataConnectionStats dataConnectionStats = new DataConnectionStats(mContext);
         dataConnectionStats.startMonitoring();
 
-        mUserManager = (UserManager) context.getSystemService(Context.USER_SERVICE);
-
         mKeepaliveTracker = new KeepaliveTracker(mContext, mHandler);
         mNotifier = new NetworkNotificationManager(mContext, mTelephonyManager,
                 mContext.getSystemService(NotificationManager.class));