Improve reclaim logging to help troubleshooting

Need better logging to help troubleshoot problems like
https://bugs.launchpad.net/nova/+bug/1193167

This change together with https://review.openstack.org/#/c/34620/
improves logging within the periodic reclaim task.

Change-Id: I3379ff2289c44b32c0406f57b4118ea23f33fb04