If the fragment needing to be reconstructed already exists, let the handoff node push it to the primary.

[Minwoo Bae]

In a previous patch (#193279), a fix was made to prevent the reconstructor from rebuilding a fragment from a list of fragments that contains itself, by omitting the response from the list. However, we should go further and prevent the reconstruction so that the handoff may push the duplicate frag to its proper location.

[John Dickinson (notmyname)]

also see http://web.ledisez.net/reconstructor-2.patch

[Tim Burke (1-tim-z)]

That patch has been submitted as https://review.openstack.org/#/c/389676/ but seems stalled... I think it's fair to say this isn't currently "In-Progress"?