add missing LTI params to ContentItemSelectionResponse message

Test Plan:
 - Do a ContentItemSelectionResponse
 - Should receive the param 'roles'

fixes PLAT-621

Change-Id: I1dc8ed1af5c237d1333eea8bad18f0dd7a74c464
Reviewed-on: https://gerrit.instructure.com/40617
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Bracken Mosbacker <bracken@instructure.com>
Product-Review: Bracken Mosbacker <bracken@instructure.com>
Reviewed-by: Nathan Mills <nathanm@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>