misc/dashboard/codereview: interpret zero reviewers as the CL being closed.
misc/dashboard/codereview: interpret zero reviewers as the CL being closed.

This is the state when the CL has been submitted by someone other than
the CL author, but before the CL author has synched their client.

R=golang-dev, rsc
CC=golang-dev
http://codereview.appspot.com/6458044

wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang