Label `rebuild/*` causes intermittent fails

[ehazlett]

A PR was "stuck" (moby/moby#30303) in that no build was triggered and when adding the rebuild/arm label the following error was thrown:

time="2017-02-13T21:41:25-05:00" level=info msg="running operation" number=30303 operation=rebuild repository="docker/docker" 
time="2017-02-13T21:41:25-05:00" level=debug msg="rejecting pull request without label \"rebuild/*\"" 
time="2017-02-13T21:41:25-05:00" level=debug msg="received GitHub event" action=unlabeled event="pull_request" number=30303 repository="docker/docker"

I could add the rebuild/* label and Gordon would remove it but nothing would happen. I even tried to add both rebuild/* and rebuild/arm but Gordon just removed the rebuild/* label and threw the error above leaving the rebuild/arm label on the issue.

My vote would be to remove the wildcard label and force people to be explicit about what they want rebuilt.