SHA256 create_stream_items strand
SHA256 create_stream_items strand

flag=none
closes VICE-2950

Test Plan:
 - Tests pass
 - Go to course with 30 enrollments or more.
 - Create an announcement, it should save without issues.

Change-Id: If497f5f2880555f080b3e59c9a53950043b0be92
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/294379
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Jeffrey Johnson <7a0f98bfe168bc29d5611ba0275e88567b492abc@instructure.com>
Product-Review: Jeffrey Johnson <7a0f98bfe168bc29d5611ba0275e88567b492abc@instructure.com>
QA-Review: Drake Harper <798ef92bc86a79e8ff768a68dc0a5fcec1d51660@instructure.com>

instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms