add stream item clearing to job if production
add stream item clearing to job if production

This was causing problems when there were too many stream item instances
that needed to be dealt with inside the transaction.

fixes LA-923
fixes LA-922
flag=none

Change-Id: Idccffb6206aaa3c8a28dd7b1be713018a5ee388e
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/234220
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: James Williams <3a5f4ed991dbfa5c9ef76ad729d240ca12f62180@instructure.com>
Reviewed-by: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
QA-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
Product-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>

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