Removed android:stopWithTask to fix lock up with QT framework

* android:stopWithTask is affecting the QT framework in an unexpected way which locks the process when closing it.
   - See QTBUG-55846 and OneSignal issue #102 for more details on the specific issue.
* Tested the flag removal on Android 4.4.2 and 6.0.1 and it had no side affects on onTaskRemoved.

OneSignalSDK/onesignal/src/main/AndroidManifest.xml

@@ -45,7 +45,7 @@
         <receiver android:name="com.onesignal.NotificationOpenedReceiver" />
         <service android:name="com.onesignal.GcmIntentService" />
 
-        <service android:name="com.onesignal.SyncService" android:stopWithTask="false" />
+        <service android:name="com.onesignal.SyncService" />
         <activity android:name="com.onesignal.PermissionsActivity" android:theme="@android:style/Theme.Translucent.NoTitleBar" />
 
         <service android:name="com.onesignal.NotificationRestoreService" />

OneSignalSDK/onesignal/src/main/java/com/onesignal/SyncService.java

@@ -98,6 +98,8 @@ public void onTaskRemoved(Intent rootIntent) {
    //   This is important as while this method is running the app will not be response if
    //   the user reopens or focuses another tasks part of the same process.
    // Also the process will be killed forcefully if this does not finish in 20 seconds.
+   // Method behavior seems unaffected by the android:stopWithTask manifest entry.
+   //   false is not required, tested on Android 4.4.2 and 6.0.1
    static void onTaskRemoved() {
       OneSignal.Log(OneSignal.LOG_LEVEL.VERBOSE, "Starting SyncService:onTaskRemoved.");
       ActivityLifecycleHandler.focusHandlerThread.stopScheduledRunnable();