adjust tests for the use-realm-roles removal

Hi Brian,

I've adjusted the `PropertiesRoleMappingTestCase` for the forthcoming `use-realm-roles` removal. This also means that the test also excersises the `<group ...>` feature of role mapping (and I've added one group exclusion too, to make that complete).

The test is passing now, so you can merge it already, but if you wish, we can do that after the `use-realm-roles` removal takes place.

Thanks!

LT