inline only usage of Array#to_csv

Change-Id: I161db686070126447603a2a511edaccec30edfef
Reviewed-on: https://gerrit.instructure.com/30028
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Zach Pendleton <zachp@instructure.com>
Product-Review: Zach Pendleton <zachp@instructure.com>
QA-Review: Stephan Hagemann <stephan@pivotallabs.com>