add info logging to destroy_session

refs: CNVS-16934

Change-Id: I5226559ff7f1ab8036567ba67fd757246b62f61e
Reviewed-on: https://gerrit.instructure.com/44803
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Nick Cloward <ncloward@instructure.com>