Check the root resource for capabilities.
Review Board 2.0 will provide the API capabilities in the root resource,

allowing RBTools to save a request. This makes that change by checking

the root before attempting to fetch the info resource.

Posted to my local server with /r/5288 applied. Saw that it fetched the

capabilities without fetching the info resource.
Posted to reviews.reviewboard.org and saw that it did fetch the info

resource.