bump switchman

also change not_ended_enrollments to be a multishard association,
since the preloader now respects the shard of the owner

test plan:
 * enroll an out-of-shard user in a course
 * do GET /api/v1/courses/:course_id/users?include[]=enrollments
 * it should include the enrollment for the out-of-shard user

Change-Id: If45f047fd12c15364076cfa7a1d3780e795e996f
Reviewed-on: https://gerrit.instructure.com/43167
Reviewed-by: Rob Orton <rob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>