I moved UserSession related tests to:
https://github.com/stianst/keycloak/blob/master/testsuite/integration/src...
The reason is that UserSession tests rely on Realms and Users so need a ModelProvider to
run. It also makes it easier to run it with different configurations.
I think we should move the rest of the tests in model/tests to the same place. This will
help once we split the model into RealmProvider and UserProvider.
If everyone is happy with this I can do it next week.