do not prompt for game when restarting after switching game, <3 @Garux

Quote by @Garux from some discord channel:

@illwieckz Houston, we've had a problem here this makes prefs dlg to prompt to restart on OK after game been choosen via small global settings dialog e2f605b1

I then said:

I guess we would be able to hack a value in config file that would tell to not display this menu on next start, this value would be reset on startup

So after switching game from within NetRadiant (or other action that just requires a restart like layout switch), NetRadiant does not display the game prompt right after having restarted, to avoid to ask for game twice, and to not bother user with a preference windows that is only expected to be displayed on fresh start, not on restart.