gameplay: fix class limit bypass from selecting class to spawn after death

this adds a check to ForceRespawn to make sure that
the player indeed can choose this class

the bypass happens because while you are still dead,
you do not count against the class limit if you select
a new class to spawn as

so, two or more players can select the same class while
dead, putting the team over the limit

Ref: ValveSoftware/Source-1-Games#2084

Author: mastercoms

src/game/server/tf/tf_player.cpp

@@ -13893,6 +13893,14 @@ void CTFPlayer::ForceRespawn( void )
 		DropFlag();
 	}
 
+	// Prevent bypassing class limits. Whoever wins on the draw can spawn as this class,
+	// and anyone who comes after will get swapped back to their old class.
+	if (!TFGameRules()->CanPlayerChooseClass(this, iDesiredClass))
+	{
+		iDesiredClass = GetPlayerClass()->GetClassIndex();
+		ClientPrint( this, HUD_PRINTCENTER, "#TF_ClassLimitReached" ); // NOTE: Add localization string 
+	}
+
 	if ( GetPlayerClass()->GetClassIndex() != iDesiredClass )
 	{
 		// clean up any pipebombs/buildings in the world (no explosions)