Fix bugs in solver_scheduler.
Fix bugs in aggregate_network_affinity_cost.
Fix Bugs in num_instances_per_host_constraint.
Optimize the num_networks_per_aggregate_constraint by simplifying the implementation a bit.
Add aggregate_image_properties_isolation, aggregate_instance_extra_specs, aggregate_multitenancy_isolation constraints matching their filter counterparts in existing filter-scheduler code.
Add server_group_affinity/anti-affinity constraints.