DNM: mailmap updates

cf:
http://wiki.ceph.com/Community/Ceph_contributors_list_maintenance_guide

Was preparing for V0.90 Ceph contributors list, using origin/next. As far as I can see, seems strictly not necessary for v0.90, but still , job is already done.

Must be mapped to **Chris Holcombe &lt;chris.holcombe@nebula.com>** in .mailmap