Test for the alpha user force starting a game

#### What's this PR do?
SMS MP games can either auto-start (which is what the already existing tests test for), or they can be manually started by the alpha user once at least one beta joins. This tests that scenario.

#### How should this be manually tested?
`$npm test` - all tests should pass.

#### Any background context you want to provide?
I'm just gonna be pushing all these PRs through because you know... short on time and such.

#### What are the relevant tickets?
More for #73