Fixed a regression where bots were still able to move while frozen.

Due to de96f9575e5c, bots are now able execute commands that allow them to move, even while they're supposed to be frozen (they should still be allowed to aim and shoot though). To fix this, at the end of a bot's tick (i.e. in CSkullBot::EndTick), double-check to see if they're supposed to be frozen, and zero out their forward/side move inputs if necessary.