Fixed: the ChangeCamera line special didn't revert the HUD back to the local player if they were spying on another player and their view changed to a non-player actor, or reverted back to them because they moved.

This addresses https://zandronum.com/tracker/view.php?id=3875 which I thought was resolved in 3.1 because of 295287439af9. Although the aforementioned commit fixed ChangeCamera not reverting the HUD to match the player being spied on, it still didn't revert the HUD back to the local player if they were already spying on another player and ChangeCamera changed the view to a non-player actor. Likewise, if the line special allowed the local player to revert the view back to themselves when they moved, it didn't revert the HUD back to them either.

This should fix those two problems, while cleaning up the code a bit. Note that cl_telespy doesn't apply when ChangeCamera is used now, not that it should've in the first place.