Set [quota]count_usage_from_placement = True in nova-next

This adds test coverage of counting quota usage for cores and ram from
placement and instances from instance mappings in the nova-next job.

Part of blueprint count-quota-usage-from-placement

Change-Id: I2eff2d60e3c227394ab137a4ec80ff21ec52c8a2

Author: melwitt

playbooks/legacy/nova-next/run.yaml

@@ -45,6 +45,8 @@
           [[post-config|$NOVA_CONF]]
           [compute]
           resource_provider_association_refresh = 0
+          [quota]
+          count_usage_from_placement = True
 
           EOF
         executable: /bin/bash