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
In the next PR I remove Entity altogether as an entity and a tag are synonymous, but I need the PR that removes GetAuthEntity from the Authorizer interface to land first.