The handleSuccessFromQueue function was missing critical steps that
exist in the legacy handleSuccess function:
1. Fetch and update the MR bead with merge_commit SHA and close_reason
2. Close the MR bead with CloseWithReason("merged", mr.ID)
Without these steps, the MR bead stayed "open" in beads even after the
queue file was deleted. This caused Mayor (which queries beads for open
merge-requests) to think there were pending MRs while Refinery (which
uses the queue) reported completion.
Fixes#46
7f9795f630