Allow the usage of the time trial track for online races.

[Macacosky]

For some gamemodes would be useful (picks off races, endurances) to have the option of using the time trial map as the playable version of the event/track. In this way, players could play tracks like Ghost Town 2 and 1 without tumbleweeds in an online race, or Downtown 1 and 2 without the traffic.