HoldingPen: exclude self from match candidates

[ksachs]

this is relevant only when re-starting a workflow

Expected Behavior

the stub-record created by a workflow should be excluded from the match candidates of itself.

Current Behavior

at some point in the workflow a stub-record is created to reserve the recid.
if the workflow is re-started after that step, this stub-record is a match candidate.
At least in cases when there is another real match candidate.

Steps to Reproduce (for bugs)

• create a literature workflow that would halt for match approval
• when it is waiting: re-start workflow

Context

a thesis was submitted twice, both waiting for selection.
After accepting one submission (https://labs.inspirehep.net/holdingpen/1257886)
I restarted the workflow of the other (https://labs.inspirehep.net/holdingpen/1257885) to get the match.
The stub-record of the submission seems to be in the match candidates.

Screenshots (if appropriate):