Patch 2.6.1: no more stuck race starts

This is a small fix for a big annoyance. When a viewer's join didn't reach the Stream Racer servers, or the connection stalled, the race could hang at the start line and never begin. That is now fixed.

What changed

• When the race starts, the game waits at most 10 seconds for joins that are still processing. Then it starts with everyone who made it.
• A join that drops out is retried automatically. If a viewer still can't be registered, they are left out of that race so everyone else can go ahead. They can type !race to join again.
• If nobody is left after that, the game reopens the lobby and resets the countdown. It no longer starts an empty race that would never finish.
• Server requests now give up after 30 seconds instead of waiting forever on a stalled connection.

Hosts, update and race on. Racers, type !race in chat when the lobby opens!