When a particular feature is marked as experimental, the feature checker

tries to determine if the user has been granted access to the feature by

way of a setting on any Local Sites the user is a member of. This can

lead to some unstable query counts as features are introduced and change

from experimental to stable, which breaks a handful of tests.
In test runs, these checks aren't really important. We're never really

going to need to check the Local Site list for a user, since we're

working under more controlled conditions. It's also just not worth the

overhead in SQL queries.
This change updates that logic to only run if not performing a test run.

It also redoes the Local Site caching logic to be more clear and to more

consistently cache results, without redundant user authentication

checks.

Unit tests pass with experimental features registered and checked during

a test run. This was tested on master, where this is a problem, but

the fix is going into 3.0.x.