Fix core member count
Fix core member count

Fix the core member count to actually work when generating a report for
multiple projects (such as all projects).

Change-Id: Ib846c5e5d42478505bd622c0f7adf105c300ed13

openstack-infra/reviewstats,JohnGarbutt/reviewstats,cp16net/reviewstats,openstack-infra/reviewstats,JohnGarbutt/reviewstats,cp16net/reviewstats