fix moodle 1.9 file importing

test plan:
* import a moodle 1.9 package with files in the
"course files" directory
* all the files should all be imported

closes #CNVS-14872

Change-Id: I90df086eac2873e05d1a9a26fb30f71464dd9814
Reviewed-on: https://gerrit.instructure.com/39511
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>