Fix green build notifier 409 reporting
Fix green build notifier 409 reporting

Summary: Previous code was subtly incorrect, but this works around the issue.

Test Plan: Manual

Reviewers: anupc

Reviewed By: anupc

Subscribers: changesbot, mkedia

Differential Revision: https://tails.corp.dropbox.com/D133341

bowlofstew/changes,dropbox/changes,dropbox/changes,wfxiang08/changes,bowlofstew/changes,dropbox/changes,bowlofstew/changes,wfxiang08/changes,wfxiang08/changes,wfxiang08/changes,dropbox/changes,bowlofstew/changes