No longer count requests to Special:CentralAutoLogin/

Requests to Special:CentralAutoLogin/ started in July 2013 and soon
became >10% of requests. However, they are only requests to log in
users, and no real page views. So we drop them.

See discussion at:
  http://lists.wikimedia.org/pipermail/wikimedia-l/2013-November/128911.html

Change-Id: I282371f0c4e49effc99d0587c2a3174532c7191b