fix sis_batch id in course activity

fixes: CNVS-13302

Fixes the sis imports to log the sis batch correctly and to display the sis
batch on the details modal in the auditing ui.

Test Plan:

- Do a SIS import for a course.
- Open the Course Activity Audit logging and the sis batch id for the course
  should be shown in the dialog.
- If the source for an event is not SIS the sis batch field will not be shown.

Change-Id: Ib93a992dac83b2ec480d888e5d4686b808bcda8f
Reviewed-on: https://gerrit.instructure.com/35475
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Product-Review: Nick Cloward <ncloward@instructure.com>