fix qti question bank selection

test plan:
* import a qti file into a course and select a question
 bank to import
* should import into the correct bank

closes #CNVS-1965

Change-Id: I4f4647cedf28b931225986b757688c8794dfa1d4
Reviewed-on: https://gerrit.instructure.com/37321
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>