state/apiserver/testing: FakeAuthorizer fixups

This PR removes three of the boolean fields on FakeAuthorizer. There is more work to be done, but this is a good point to land what I have done so far.

Discussion: https://lists.ubuntu.com/archives/juju-dev/2014-July/003104.html
This test made no sense. NewUserManagerAPI can only be called with an authoerizer that represents a user, any other authorizer will return ErrPerm, but this was not previously checked on line 290