Clients now update their ping during intermissions and won't timeout when the server receives their response.

This is supposed to address https://zandronum.com/tracker/view.php?id=4379. I'm not sure if there was ever a specific reason why the server doesn't send ping commands to clients during intermissions, but since clients aren't sending commands as frequently as they do while in a level, the server will think they're lagging when they aren't. If the intermission goes on long enough, then when the next level begins, everyone will look like they're lagging very briefly, which can give people the wrong idea.

Since very little bandwidth is consumed during intermissions, sending ping commands once per second shouldn't be an issue and ensures everyone's pings are updated and still relevant, which can be a good thing. I made it so that receiving CLC_PONG commands updates the client's "last command tick" so they don't timeout. I don't suppose this is an issue either. If we're receiving this command from the client regularly, then they shouldn't timeout, right (I also can't think of how this could be abused)?

All of this means that there's no reason to redact the lagging icon from the scoreboard during intermissions. It would be useful to know who's actually lagging during this state.