Android: don't directly access m_qtThread member

Task-number: QTBUG-118077
Change-Id: I2103483a2bfa8abe9be832790611b07a5d011f76
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>

src/android/jar/src/org/qtproject/qt/android/QtActivityBase.java

@@ -147,7 +147,7 @@ public class QtActivityBase extends Activity
         if (!m_retainNonConfigurationInstance) {
             QtNative.terminateQt();
             QtNative.setActivity(null);
-            QtNative.m_qtThread.exit();
+            QtNative.getQtThread().exit();
             System.exit(0);
         }
     }

src/android/jar/src/org/qtproject/qt/android/QtApplicationBase.java

@@ -9,7 +9,7 @@ public class QtApplicationBase extends Application {
     @Override
     public void onTerminate() {
         QtNative.terminateQt();
-        QtNative.m_qtThread.exit();
+        QtNative.getQtThread().exit();
         super.onTerminate();
     }
 }

src/android/jar/src/org/qtproject/qt/android/QtNative.java

@@ -42,7 +42,7 @@ public class QtNative
     private static final ArrayList<Runnable> m_lostActions = new ArrayList<>();
     private static boolean m_started = false;
 
-    public static QtThread m_qtThread = new QtThread();
+    private static final QtThread m_qtThread = new QtThread();
     private static ClassLoader m_classLoader = null;
 
     private static final Runnable runPendingCppRunnablesRunnable = new Runnable() {

src/android/jar/src/org/qtproject/qt/android/QtServiceBase.java

@@ -35,7 +35,7 @@ public class QtServiceBase extends Service {
         QtNative.quitQtCoreApplication();
         QtNative.terminateQt();
         QtNative.setService(null);
-        QtNative.m_qtThread.exit();
+        QtNative.getQtThread().exit();
         System.exit(0);
     }