improve qti associate interaction parsing

test plan:
* import the package referenced in the ticket
* the matching questions should list matches properly

fixes #CNVS-1617

Change-Id: I40a91e1916392cdc92c4a4f01ff3a1b99c35c735
Reviewed-on: https://gerrit.instructure.com/36524
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>