add some missing fields to sis batch api

you can set these fields when creating a batch
and it'd be convenient to get them back to auditing
and debugging

Test Plan:
 * GET an SIS Batch from the api, these fields should be set:
   batch_mode
	 batch_mode_term_id
	 override_sis_stickiness
	 add_sis_stickiness
	 clear_sis_stickiness

closes CNVS-15236

Change-Id: Ia26e582dcc90efb6d7877e39fb2d238fe2f22c9f
Reviewed-on: https://gerrit.instructure.com/40463
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Tyler Pickett <tpickett+gerrit@instructure.com>
Product-Review: Tyler Pickett <tpickett+gerrit@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>