Fix qt5 sync

On Qt5 low and empty states stops syncing and forward signal opened network session out from NetworkManager as connectionSuccess.

Forward signaled connectionSuccess() is connected to slotNetworkSessionOpened. The slotNetworkSessionOpened need to be called to get scheduled sync running. The slotNetworkSessionOpened should also get called by state change handle of NetworkManager.cpp. However, stateChange signal originates from QNetworkSessionPrivate that is created by QBearerEngine (createSessionBackend) -- plugins. Thus, it's not guaranteed that all states are always triggered similarly.