Qubes().domains.refresh_cache() tries to preserve cached VM objects if
the class matches - this way if an application keeps reference to any,
it will still be the same as freshly obtained from the collection, and
also it will receive cache updates/invalidates based on events.
The check for class change was invalid - on core-admin-client side we
have just one QubesVM class with 'klass' attribute. This leads to VM
objects being disconnected from VMCollection and stale properties cache
there (because they no longer receive events).
Fix the check.
And also add a test if indeed the same object is returned.
45a28c29ae