Code review comment for ~ltrager/maas:limit_listing_queries

Thanks for the review. We never had query_count tests for get(), only list(). The reason get() takes so many more queries then list() is due to storage and network interface dehydration. Get queries have gone down with this branch. get() on the MachineHandler went from 61 queries to 48.

I was relying on the query_count tests to test get_queryset, I've added explicit tests for get_queryset.