Revert "Don't run Quit() twice during startup"
This reverts commit b9fc3584.
the aboutToQuit signal is emitted just before the app closes and gives chance to run some teardown routines, when closing the app via a keyboard shortcut cmd+q on macOS or alt+f4 on linux we get this signal and the handler stops the firewall and perform other needed cleanup
removing this causes a bug where quiting the app would keep the firewall running which results into no internet access