Core model test of host.xml paths are messed up

While working on https://github.com/wildfly/wildfly-core/pull/2163 Paul Ferraro noticed that HostSpecifiedPathsTestCase was creating a Resource for which there was no corresponding MRR, which his fix then had to handle. Doing that is wrong so I went to clean it up and found that the tests in this package are using incorrect model structures. So I'll clean that up.