Bug 1093743 retrigger fix

I confirmed this fix with these two resultsets:
http://local.treeherder.mozilla.org/ui/#/jobs?repo=mozilla-inbound&tochange=a2551ec63d3c&searchQuery=os%20x%2010.8%20debug&fromchange=49d26513f6be

On the old code, when I retriggered the red build from change a2551ec63d3c, the retrigger showed in change 49d26513f6be.  With the new code, it showed in the first change a2551ec63d3c.