Fix NPE in tethering startup

mUserManager should be ready before #makeTethering because mTethering may
call isTetheringSupported which need to reference mUserManager

Bug: 148642028
Test: build
Change-Id: I100b5d6cc8f49640c33fa930b819033de5d6492c

packages/Tethering/src/com/android/server/connectivity/tethering/TetheringService.java

@@ -77,8 +77,8 @@ public class TetheringService extends Service {
         mLog.mark("onCreate");
         mDeps = getTetheringDependencies();
         mContext = mDeps.getContext();
-        mTethering = makeTethering(mDeps);
         mUserManager = (UserManager) mContext.getSystemService(Context.USER_SERVICE);
+        mTethering = makeTethering(mDeps);
     }
 
     /**