misc/dashboard/codereview: add admin-only link to force-update a CL.
misc/dashboard/codereview: add admin-only link to force-update a CL.

R=nigeltao
CC=golang-dev
http://codereview.appspot.com/6431055
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go