qt: implement FutureScheduler, always await async code to complete

src/daemon/DaemonManager.h

@@ -33,6 +33,7 @@
 #include <QUrl>
 #include <QProcess>
 #include <QVariantMap>
+#include "qt/FutureScheduler.h"
 #include "NetworkType.h"
 
 class DaemonManager : public QObject
@@ -71,6 +72,8 @@ public slots:
 
 private:
     explicit DaemonManager(QObject *parent = 0);
+    ~DaemonManager();
+
     static DaemonManager * m_instance;
     static QStringList m_clArgs;
     QProcess *m_daemon;
@@ -79,6 +82,7 @@ private:
     bool m_has_daemon = true;
     bool m_app_exit = false;
 
+    FutureScheduler m_scheduler;
 };
 
 #endif // DAEMONMANAGER_H