implement a spec test that tests the oar property generator on a fake cluster with disks

tests/oar_properties_spec.rb

...s/stub_oar_properties/dump_oar_api_configured_server.json

..._properties/dump_oar_api_configured_server_with_disk.json

tests/stub_oar_properties/dump_oar_api_empty_server.json

...stub_oar_properties/load_data_hierarchy_stubbed_data.json

...roperties/load_data_hierarchy_stubbed_data_with_disk.json