The addition of public local sites exposed a bunch of assumptions in the user

linking. By default, the user resource within a local site only contains those

users who are actually members of the site. This causes a bunch of bizarre bugs

in rbtools or other consumers of the API, because the links between objects

(such as the review request submitter) could be 404.
This change makes it so that if a local site is public, all users on the server

are exposed in the site's user resource.

Verified that links no longer 404 using cURL. I intend to add a unit test for

this when porting to 2.0.x (since the API testing framework there is much

improved over 1.7.x's)