Ignore non-voting jobs in gerrit

We shouldn't be reporting back to users why a non-voting job is failing,
Non-voting jobs are non-voting because the are unstable, so we don't want
folks running recheck on a bug for a non-voting job.

Update the unit tests to cover this case.

Change-Id: I61f4e7bb28235d2974f3dcf70187437c80f918d3